An attacker exploited a previously unknown and unpatched Cisco vulnerability earlier this year to infiltrate a communications service provider and gain the highest level of access possible, Mandiant said Wednesday.

Cisco has since patched the flaw, one of seven actively exploited zero-day vulnerabilities this year in its SD-WAN (software-defined wide area network) software used to manage internet traffic within organizations, typically those that are widely distributed, such as banks with numerous branches.

But Google-owned cybersecurity firm Mandiant said the attacker (or attackers) could have used its root-level access to obtain broad and undetected visibility into the internal traffic throughout the provider’s entire corporate network. In a caveat, Mandiant also said it could not fully assess how far the compromise actually went because of how cleverly the perpetrators hid their activity.

The attack illustrated hackers’ ongoing targeting of edge devices, Mandiant said. Attacks on such devices have been very common and involved in some of the most consequential breaches in recent years, prompting the Cybersecurity and Infrastructure Agency to direct federal agencies to give them special attention this year.

“This campaign underscores the living off the edge paradigm, where threat actors prioritize the compromise of network appliances to bypass traditional security perimeters,” Mandiant wrote in a blog post. “As organizations increasingly adopt software-defined networking, the orchestrators managing these environments become primary targets. These devices offer a black box environment for threat actors: they often lack the telemetry required for deep forensic analysis, and their role as a central control plane provides a stealthy platform for persistent, wide-scale access to internal enterprise traffic.”

Mandiant didn’t attribute the attack to any specific group, citing the work the attacker did to cover their tracks and delete evidence. But it noted that “for state-sponsored actors, the ability to exploit zero-day vulnerabilities in these platforms remains a premier vector for long-term strategic intelligence collection.”

Kelli Vanderlee, senior manager for Google Threat Intelligence Group, told CyberScoop that “exploiting zero day vulnerabilities in edge devices and the extensive anti-forensic activities are consistent with previously documented cyber espionage threat actor behavior.”

The company also didn’t name the victim service provider.

The attacks on the service provider came in two waves. The first activity Mandiant observed from late 2025 to early 2026 exploited one of two then-unpatched vulnerabilities (CVE-2026-20127 or CVE-2026-20182), with the attacker making unauthorized “peering” connections to the victim’s SD-WAN Manager devices in a kind of digital handshake to verify identity and trust.

Once there, the attacker facilitated its access and used it to manipulate default account passwords in hopes of avoiding detection. Next, the attacker exploited the zero-day vulnerability (CVE-2026-20245) in Cisco Catalyst SD-WAN Manager, activity Mandiant observed in March, and created a rogue user account, “troot” that gave full root-level control.

“On June 4, 2026, Cisco published a security advisory about a privilege escalation vulnerability in Cisco Catalyst SD-WAN Manager,” a Cisco spokesperson said. “Cisco strongly recommends customers upgrade to a fixed software release as outlined in the advisory.”

Updated 6/24/26: to include Cisco comment.

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Researchers and threat hunters are scrambling to respond to an actively exploited authentication-bypass vulnerability affecting Palo Alto Networks customers’ firewalls. 

The company initially tagged CVE-2026-0257 with a medium-severity rating when it disclosed the defect May 13, but quickly reassessed it as critical after Rapid7 observed and confirmed active exploitation in the wild. The Cybersecurity and Infrastructure Security Agency followed suit, and added the vulnerability to its known exploited vulnerabilities catalog Friday.

The escalated threat posed by the defect, which allows remote attackers to bypass security restrictions and establish a VPN connection to an affected firewall, showcases how quickly a seemingly mild vulnerability can turn into an urgent warning. 

“Palo Alto Networks is actively monitoring limited exploitation attempts targeting CVE-2026-0257 on unpatched PAN-OS devices where mitigations have not been applied,” a company spokesperson said in a statement. The company on Friday urged all customers to immediately apply the patch or follow its recommended steps for mitigation. 

The vendor and Rapid7, which first observed exploitation May 17 in a customer environment, declined to say how many organizations are impacted thus far. Yet, Douglas McKee, director of vulnerability intelligence at Rapid7, warned: “We’ve continued to see new victims roll in, including a couple of customers hit within just an hour of each other during a second wave of activity” on May 21. 

Jake Knott, security researcher at watchTowr, told CyberScoop the vulnerability and resulting exploits follows a recurring trend wherein attackers target exposed network edge devices and rapidly identify, develop and weaponize exploits for initial access. 

“This is yet another authentication bypass on a device whose sole job is to guard the front door to an organization’s network,” he said. “What stands out is how simple it is — an attacker can forge a valid authentication cookie using nothing more than the appliance’s publicly available TLS certificate. The entire exploit is a single HTTP request.”

The vulnerability has a few requisites that limit exposure, specifically posing risk to some Palo Alto Networks customers running GlobalProtect portal or gateway configured to enable authentication override cookies. 

“The cookie encryption and decryption certificate must be reused with another feature, which potentially exposes the public key for that certificate,” said Caitlin Condon, vice president of security research at VulnCheck.

“It’s difficult to say how many deployments meet those criteria for exploitability, but Palo Alto Networks firewalls have a very large footprint, which means even uncommon configurations can present significant attack surface area,” she added.

Rapid7 said the same attacker or group is likely responsible for both waves of exploitation last month, but in many cases attackers are not establishing a full VPN connection or moving to other parts of the impacted network. 

The attackers are “highly opportunistic and clearly monitor the security research community,” McKee said. “Attackers are purposefully weaponizing medium-severity vulnerabilities, which are typically lower priority or blind spots for organizations.”

Multiple threat clusters are swarming to the opportunity and quickly adapting to published research.  Researchers have not attributed the malicious activity to any specific threat groups. 

“Their exact origins and long-term objectives remain unclear, as they currently seem focused purely on opportunistic initial access rather than targeted, long-term espionage,” McKee said. 

Palo Alto Networks said it discovered the vulnerability internally through its use of frontier AI tools. Yet, within days of its public disclosure, initial assessments were proven inadequate.

“This is a pattern we continue to see — the urgency only arrives after exploitation is underway,” Knott said. “Organizations that wait for confirmation of active exploitation before patching will consistently find themselves reacting too late.”

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ON SECURITY By Susan Bradley The “edge,” by which I mean the network hardware standing between the Internet and the PCs and devices on your network, is a first line of defense against attackers. What’s on your edge? At any point during the day, attackers are out to get someone. You may not be the […]

Attackers are hitting Ivanti customers yet again — circling back to a common target and consistently susceptible vendor in the network edge space — by exploiting a zero-day vulnerability in one of the company’s most besieged products. 

Ivanti warned customers that attackers have successfully exploited CVE-2026-6973, an improper input validation defect in Ivanti Endpoint Manager Mobile (EPMM) that allows authenticated users with administrative privileges to run code remotely. The company alerted customers to the threat in a security advisory Thursday while also disclosing four additional high-severity vulnerabilities in the same product.

“At the time of disclosure, Ivanti is aware of very limited exploitation in the wild of CVE-2026-6973, which requires authenticated administrative access to implement,” a spokesperson for Ivanti said in a statement.

Ivanti did not say when the first instance of exploitation occurred, or precisely how many customers have already been impacted.

The Cybersecurity and Infrastructure Security Agency added the zero-day to its known exploited vulnerabilities catalog within hours of Ivanti’s disclosure.

The company released patches for all five vulnerabilities Thursday, including the four additional defects — CVE-2026-5787, CVE-2026-5788, CVE-2026-6973 and CVE-2026-7821 — which it said haven’t been exploited in the wild.

“Ivanti discovered these vulnerabilities in recent weeks through internal detection processes which are supported by advanced AI, customer collaboration, and responsible disclosure,” the company spokesperson said. One of the defects was discovered and responsibly reported to Ivanti by a former employee.

The company suggested at least one of the root causes for the latest zero-day may be traced to lingering risk posed by a pair of separate, critical zero-days — CVE-2026-1281 and CVE-2026-1340 — that were exploited starting in late January. The fallout from those exploited vulnerabilities in Ivanti EPMM spread to nearly 100 victims, including The Netherlands’ Dutch Data Protection Authority and the Council for the Judiciary, by early February.

The latest Ivanti EPMM zero-day “requires authenticated administrative access to exploit, which is why customers who followed Ivanti’s recommendation in January to rotate EPMM credentials are at significantly reduced risk. Customers unaffected by the prior vulnerability are also at a much lower risk,” the company spokesperson said.

Caitlin Condon, vice president of security research at VulnCheck, said the administrative privileges required to exploit CVE-2026-6973 indicates it was possibly exploited as part of an attack chain relying on another method for initial access. 

“No attribution was shared on threat actor exploitation of CVE-2026-6973, but two other 2026 CVEs in Ivanti EPMM — CVE-2026-1281 and CVE-2026-1340 — have been exploited by a range of threat actors, including China- and Iran-attributed groups,” Condon told CyberScoop. 

“Those vulnerabilities notably were code-injection vulnerabilities that were remotely exploitable without authentication, unlike CVE-2026-6973,” she added. “Both CVE-2026-1281 and CVE-2026-1340 appear to have been fixed in today’s Ivanti release. Comparatively, these earlier vulns were of higher initial concern than today’s fresh zero-day vulnerability, which requires admin authentication.”

Attacks involving Ivanti defects are a recurring problem for the vendor’s customers and security practitioners at large, including many vulnerabilities that attackers exploited before the company caught or fixed the errors. 

The Cybersecurity and Infrastructure Security Agency has flagged 34 Ivanti defects on its known exploited vulnerabilities catalog since late 2021. At least 22 defects across Ivanti products have been exploited in the past two years, including five vulnerabilities in Ivanti EPMM in the last year.

During an interview with CyberScoop in March at the RSAC Conference, Ivanti Chief Security Officer Daniel Spicer said the company’s transparency partly explains the high number of vulnerabilities reported and disclosed in its products. 

“My position here at Ivanti is it doesn’t do our customers any good to be quiet about this,” he said, describing the company’s communication stance with the public, CISA and global partners as “very aggressive.”

That’s not always the case with other vendors, Spicer said. “I don’t know that transparency is a core tenant of all other organizations.”

The company, which serves many government agencies and critical infrastructure operators, also routinely notes that highly skilled and resourced attackers, including those backed by nation-states, are often responsible for these waves of attacks on its customers.

Ivanti maintains that it’s trying to consistently improve the security of its products. “Through continued investment in its product security program, including the use of advanced AI paired with human verification, Ivanti is strengthening its ability to identify, remediate, and disclose issues quickly, helping customers stay ahead of an increasingly compressed threat landscape,” the spokesperson said.

The way Spicer put it in March: “We want to make sure that people understand that we are trying to do the right thing.”

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A state-sponsored hacking group has implanted a custom backdoor on Cisco network security devices that can survive firmware updates and standard reboots, U.S. and British cybersecurity authorities disclosed Thursday, marking a significant escalation in a campaign that has targeted government and critical infrastructure networks since at least late 2025.

The Cybersecurity and Infrastructure Security Agency and the United Kingdom’s National Cyber Security Centre jointly published a malware analysis report identifying the backdoor, code-named Firestarter. Cisco’s threat intelligence division, Talos, attributed the malware to a threat actor it tracks as UAT-4356. The company attributed the same group to a 2024 espionage campaign called ArcaneDoor, which focused on compromising network perimeter devices.

CISA confirmed it discovered Firestarter on a U.S. federal civilian agency’s Cisco Firepower device after identifying suspicious connections through continuous network monitoring. The finding prompted an updated emergency directive issued Thursday, requiring all federal civilian agencies to audit their Cisco firewall infrastructure and submit device memory snapshots for analysis by Friday.

A backdoor that outlasts patches

The central concern driving the updated directive is the attack group’s ability to persist on compromised devices, even after enterprises applied security patches Cisco released in September 2025. Those patches addressed two vulnerabilities — CVE-2025-20333, a remote code execution flaw in the VPN web server component, and CVE-2025-20362, an unauthorized access vulnerability — that UAT-4356 exploited to gain initial entry. According to CISA, devices compromised before patching may still harbor the implant.

Firestarter allows attackers to achieve persistence by manipulating the Cisco Service Platform mount list, a configuration file that governs which programs execute during the device’s boot sequence. When the device receives a termination signal or enters a reboot, the malware copies itself to a secondary location and rewrites the mount list to restore and relaunch itself after the system comes back online. 

Critically, a standard software reboot does not remove the implant. Only a hard reboot — physically disconnecting the device from its power supply — is sufficient to clear the persistence mechanism from memory, according to both CISA and Cisco.

From there, the malware injects malicious shellcode into LINA, the core networking and firewalling code of Cisco’s Adaptive Security Appliance and Firepower Threat Defense software. Once embedded, the malware intercepts a specific type of network request normally used for VPN authentication. When a request arrives containing a hidden trigger sequence, it executes code supplied by the attackers, giving them a backdoor into the device.

Ties to ongoing campaign

Cisco Talos noted that Firestarter shares significant technical similarities with a previously documented implant called RayInitiator, suggesting the tools share a common origin or development history within UAT-4356’s arsenal.

In the federal agency incident analyzed by CISA, the attackers first deployed a separate implant, called Line Viper, to gain access to device configurations, credentials, and encryption keys. Firestarter was installed shortly after, prior to Cisco’s September 2025 patches being applied to those specific devices. When the agency patched its systems, Firestarter stayed on the devices, and the actors used it to then redeploy Line Viper in March, nearly six months after the initial breach.

Cisco and CISA did not attribute the espionage attacks to a specific nation state, but Censys researchers previously said it found compelling evidence indicating a threat group based in China was behind the ArcaneDoor campaign. Censys noted it found evidence of multiple major Chinese networks and Chinese-developed anti-censorship software during its investigation into the early 2024 attacks.

The persistence vulnerability affects a broad range of Cisco hardware, including the Firepower 1000, 2100, 4100, and 9300 series, as well as the Secure Firewall 1200, 3100, and 4200 series.

Cisco has released updated software to address the persistence mechanism, though the company strongly recommends reimaging affected devices rather than relying solely on software updates where compromise is suspected.

The incident reflects a pattern increasingly seen among state-linked hackers: targeting the network edge devices that organizations rely on to enforce security boundaries. Because these appliances sit at the perimeter of enterprise and government networks, compromising them can expose internal traffic and give attackers a position to intercept credentials and communications.

CISA acknowledged active exploitation of the underlying vulnerabilities was ongoing at the time of publication.

A Cisco spokesperson told CyberScoop that customers needing assistance should contact Cisco Technical Assistance for support. CISA did not respond to a request for comment. 

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Attackers rarely exploit an edge-device vulnerability indiscriminately. Typically, they first test how widely the flaw can be used and how much access it can provide, then move on to steal data or disrupt operations.

Pre-attack surveillance and planning leaves a lot of noise in its wake. These signals — particularly spikes in traffic that are hitting specific vendors — can act as an early-warning system, often preceding public vulnerability disclosures, according to research GreyNoise shared exclusively with CyberScoop prior to its release. 

Roughly half of every activity surge GreyNoise detected during a 103-day study last winter was followed by a vulnerability disclosure from the same targeted vendor within three weeks, GreyNoise said in its report.

Researchers determined that the median warning of an impending vulnerability disclosure arrived nine days before the targeted vendor issued a public alert to its customers.

“Virtually every time we see large scale spikes in reconnaissance and inventory activity looking for a certain device, it’s because somebody knows about a vulnerability,” Andrew Morris, founder and chief architect at GreyNoise, told CyberScoop.

“Within a few days or weeks — usually within the responsible disclosure timeline — a new very bad vulnerability comes out,” he added.

GreyNoise insists that every day of advance notice matters, giving defenders an opportunity to defend against and thwart potential attacks before they occur. 

The real-time network edge scanning platform spotted 104 distinct activity surges across 18 vendors during its study period. These embedded systems, including routers, VPNs, firewalls and other security systems, consistently account for the most commonly exploited vulnerabilities.

“Attackers love hacking security devices like security appliances. The irony of that is just not lost on me at all,” Morris said.

“It hasn’t gotten bad enough for us to start taking the security of these devices seriously,” he added. “It’s not bad enough for us to take it seriously enough to start ripping these things out and replacing them with new devices or new vendors.”

GreyNoise linked traffic surges to a swarm of vulnerabilities disclosed by vendors across the market, including Cisco, Palo Alto Networks, Fortinet, Ivanti, HPE, MicroTik, TP-Link, VMware, Juniper, F5, Netgear and others.

“It’s becoming scientifically empirical, and it’s becoming more like meteorology than mysticism,” Morris said. “This is like clockwork now.”

GreyNoise breaks these traffic surges down to measure intensity and breadth. Session counts indicate how hard existing sources are hammering a specific vendor and unique source IP counts demonstrate how widely new infrastructure is joining the activity, researchers wrote in the report.

“When both the intensity and breadth of targeting increase simultaneously, it signals a coordinated escalation,” the report said. 

“When you see a session spike against one of your vendors and new source IPs joining at the same time, treat it as a high-confidence reason to look harder. When you see only an IP spike, do not assume a vulnerability is coming,” researchers added. 

The study bolsters other research from Verizon, Google Threat Intelligence Group and Mandiant — landing during what GreyNoise calls “the most aggressive period of edge device exploitation on record.”

This activity doesn’t happen in a vacuum and threat groups aren’t flooding edge devices with traffic for free or for fun, according to Morris.

“People tend to treat internet background noise like it’s this unexplainable phenomenon,” he said. “They’re clearly trying to test the existence of a vulnerability in order to compromise the systems.”

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Just the other day, the United States Federal Communications Commission (FCC) updated its list of products that can’t be sold in the US to include all consumer routers made in foreign countries. It’s a big — but potentially disruptive — move to limit supply-chain security risks to US networks. Now mind you, while I can […]

Researchers and threat hunters are scrambling to contain a maximum-severity defect in Ubiquiti’s UniFi Network Application that attackers could exploit to take over user accounts by accessing and manipulating files.

The path-traversal vulnerability — CVE-2026-22557 — affects software used to manage UniFi networking devices, including access points, gateways and switches. The vendor disclosed and released patches for the defect in a security advisory Wednesday.

“As of this morning, we have not observed any public proof-of-concept exploits or confirmed reports of exploitation in the wild,” Matthew Guidry, senior product detection engineer at Censys, told CyberScoop.

“However, because this is a path-traversal vulnerability, the technical complexity for an attacker is typically lower than memory-corruption or buffer-overflow bugs,” he added. “Given that the CVSS 10 rating implies low attack complexity, we anticipate that once the specific vulnerable endpoint is identified, exploitation will be trivial to automate.”

Censys sensors observed nearly 88,000 UniFi Network Application hosts publicly exposed to the internet as of Friday morning. The software doesn’t expose what version it’s running, so scans cannot distinguish between vulnerable and patched instances.

Roughly one-third of the exposed instances of UniFi Network Application are located in the United States. 

As a defender, when you see a CVSS 10 for a product you immediately recognize and know is everywhere, you probably get a bit anxious,” Guidry said. “You also know it’s remotely exploitable, requires no authentication, and needs no user interaction, because it wouldn’t be a 10 if it wasn’t. Ubiquiti is a name you hear frequently, and many of those devices are sitting directly on the internet.”

Ubiquiti advises UniFi Network Application users to update to the latest software versions, which also addressed a second vulnerability — CVE-2026-22558 — that attackers could exploit to escalate privileges.

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