Researchers said INC ransomware, one of the most active ransomware groups globally, has been the main attacker exploiting a pair of SonicWall zero-days soon after they were disclosed last month.

The prolific ransomware-as-a-service operation wasn’t the first group to exploit the flaws, which were actively exploited for three weeks before the vendor disclosed and patched the defects July 14, but it has been the most assertive and concerning group to target and chain both vulnerabilities together for full access.

“Since public disclosure, INC ransomware has emerged as the most commonly named threat actor actively weaponizing this vulnerability chain,” Brett Deroche, director of incident response at Rapid7, told CyberScoop. “While Inc is the name driving the post-disclosure wave, we can’t attribute the full body of exploitation to INC specifically.”

SonicWall did not respond to a request for comment.

The SonicWall vulnerabilities — CVE-2026-15409 and CVE-2026-15410 — are the latest in a series of security issues confronting the vendor’s customers, including actively exploited zero-days, previously disclosed defects, and an attack last year that allowed a state-sponsored threat group to steal the firewall configurations of every SonicWall customer. 

Just last week, Huntress researchers spotted an attack spree that compromised 30 SonicWall customers in less than two days. 

Ransomware groups have taken a special interest in SonicWall. Ten of the 17 SonicWall defects added to the Cybersecurity and Infrastructure Security Agency’s known exploited vulnerabilities (KEV) catalog since late 2021 are known to be used in ransomware campaigns.

INC ransomware, which has claimed nearly 900 victims across 71 countries since it was first discovered three years ago, is just the latest financially-motivated group to target SonicWall customers. 

Researchers haven’t determined how many organizations have been impacted by the latest SonicWall zero-days, including attacks linked to INC ransomware. 

“Attribution here isn’t a single clean answer. The earliest exploitation we observed, beginning June 22, traced back to common hosted infrastructure, though those attacks were largely unsuccessful,” Deroche said. 

“INC’s confirmed activity that we’ve observed came after public disclosure, using different infrastructure and moving from initial access to ransomware deployment in short order. That’s a meaningfully different operational tempo and skill level than what we saw pre-disclosure,” he added. 

Deroche said Rapid7 has successfully prevented data theft and encryption in the majority of recent cases, yet noted ransomware was deployed in at least one case the security vendor observed.

Yet, there could be other attacks outside the purview of Rapid7’s telemetry. INC ransomware has listed multiple new alleged victims on its data leak site, including organizations and government agencies in Australia, the United States, the United Arab Emirates, Colombia and Switzerland, Resecurity said in a blog post Saturday.

The company said it has aided several victims with incident response, and learned multiple victims received emails and phone calls from alleged hackers who pressured them to engage in negotiations.

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Huntress researchers spotted an active and ongoing series of attacks targeting SonicWall VPN and firewall accounts, which compromised 30 organizations in less than two days, the company said in a threat advisory Tuesday.

The credential stuffing campaign started Saturday and grew rapidly, ultimately compromising 92 unique user accounts during the next 41 hours, according to Huntress. Researchers said the attacks were broad and opportunistic, hitting various SonicWall devices, rather than targeting specific types of organizations.

SonicWall hasn’t released a security advisory about the malicious activity as of press time. A spokesperson told CyberScoop the company is still investigating and hopes to have more information soon.

The attacks ended — at least for now — as abruptly as they began. The last compromise occurred Monday, according to Michael Tigges, principal tactical response analyst at Huntress.

“This fits campaign trends,” he said. “A rash of compromise will break out, followed by silence until the adversary rotates infrastructure.”

Attackers, which haven’t been identified, have also refrained from initiating any post-compromise activity, indicating the intrusions could be pre-positioning for future attacks. 

“With local network access, the sky is essentially the limit for most networks that do not have proper topology controls in place,” Tigges said.

Huntress’ observations are limited to telemetry it collects from its customers, meaning all of the identified victims were Huntress customers using SonicWall devices, so the number of organizations impacted could be greater. 

Researchers haven’t identified a root cause for the attacks, noting that they begin with authorized logins. Attackers are validating credentials against remote access portals to compromise as many vulnerable accounts as possible, the cybersecurity vendor and threat intelligence firm said. 

“This could be an aggregation of stealer malware logs, previously compromised SonicWall configuration files, or historic CVE compromise that resulted in more credentials than the adversary could use at the time,” Tigges said. 

In 2025, an undisclosed state-sponsored threat actor intruded SonicWalls’s cloud environment and stole firewall configurations of every customer. 

SonicWall customers have also been hit by a barrage of actively exploited zero-days, including a pair of zero-days that were exploited for three weeks before the vendor disclosed and patched the defects earlier this month, and previously disclosed defects in SonicWall devices for years. 

Seventeen defects affecting the vendor’s products have been added to CISA’s known exploited vulnerabilities catalog since late 2021. Ten of those defects are known to be used in ransomware campaigns, according to CISA, including a wave of about 40 Akira ransomware attacks between mid-July and early August 2025.

“Edge devices are one of the most targeted interfaces, comprising over 70% of active intrusions triaged by Huntress, including the overwhelming majority of ransomware deployments,” Tigges said. “Organizations that do not spend significant time architecting secure remote access solutions and networks that are resilient to edge-device compromise will likely continue to feel the burn in the coming months and years.”

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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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Attackers are actively exploiting a zero-day vulnerability affecting some Palo Alto Networks’ customers’ firewalls, the security vendor said in an advisory Tuesday.

The critical memory corruption vulnerability — CVE-2026-0300 — affects the authentication portal of PAN-OS, and allows unauthenticated attackers to run  code with root privileges on the vendor’s PA-Series and VM-Series firewalls, the company said.

Palo Alto Networks did not say when or how it became aware of active exploitation, nor when the earliest known exploitation occurred. The Cybersecurity and Infrastructure Security Agency added the defect to its known exploited vulnerabilities catalog Wednesday.

The company hasn’t released a patch for the vulnerability or described the scope and objective of confirmed attacks.

“This vulnerability is specific to a limited number of customers with their User-ID Authentication Portal (Captive Portal) exposed to the public internet or untrusted IP addresses. We have observed limited exploitation of this issue and are working to release software fixes, with the first updates expected to be available on May 13,” a Palo Alto Networks spokesperson told CyberScoop.

The company said firewalls exposed to the buffer-overflow vulnerability, which has a CVSS rating of 9.3, are broadly exposed in real-world deployments, and it described the attack complexity as low.

Shadowserver scans found more than 5,800 publicly exposed VM-Series firewalls running PAN-OS as of Tuesday, yet it’s unknown how many of those instances have restricted authentication access to trusted internal IP addresses or disabled the feature altogether.

“We have provided clear mitigation guidance to our customers to secure their environments immediately. This issue does not impact Cloud NGFW or Panorama appliances. We remain committed to a transparent, security-first approach to protect our global customer base,” Palo Alto Networks’ spokesperson added.

Benjamin Harris, CEO and founder of watchTowr, noted that Palo Alto Networks proactively alerted customers to the zero-day, a step that allowed defenders to take action on potentially exposed instances. 

“In a bad situation, that is the best they can do immediately. However, that also alerts everyone to the existence of a vulnerability,” he told CyberScoop.

Despite the risk, Harris said watchTowr expects attacks linked to the zero-day exploit to be “very limited.” 

Palo Alto Networks and its impacted customers remain the only parties to have observed exploitation in the wild, but researchers warn that will likely change soon. 

“It’s likely rules will also start to fire in third-party organizations and honeypots shortly,” Caitlin Condon, vice president of security research at VulnCheck, told CyberScoop. 

“Management interfaces, login pages, and authentication portals have been common adversary targets for both opportunistic and targeted campaigns in recent years,” she added. “With researcher and community eyes on the vulnerability, it’s likely that we’ll see public exploits and broader exploitation quickly, provided the issue isn’t prohibitively difficult to exploit.”

Palo Alto Networks has yet to attribute the attacks to any known threat group, publish indicators or compromise, nor disclose the type of organizations that have been targeted and impacted. 

Researchers are hunting for malicious activity and advise customers to apply patches upon release.

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