Attackers of unknown origins and motivations are exploiting a critical zero-day vulnerability in Cisco Secure Email Gateway, authorities and researchers said Monday.

The vulnerability — CVE-2026-76461 —  was exploited before Cisco disclosed and patched the defect Monday and allows unauthenticated, remote attackers to execute commands with root privileges on vulnerable systems. “In practical terms, that gives the attacker control of the gateway itself,” Douglas McKee, director of vulnerability intelligence at Rapid7, told CyberScoop.

Cisco said its product security incident response team became aware of active exploitation of the defect affecting Cisco AsyncOS Software for Cisco Secure Email Gateway in September. When asked for further details, a company spokesperson pointed to the advisory and reiterated that the company is aware of active exploitation of the vulnerability.

The company did not say how many organizations are impacted by active exploitation thus far, but it indicated multiple customers were likely compromised prior to disclosure. 

“Cisco has conducted a thorough threat intelligence investigation on devices that belong to Cisco Secure Email Cloud. Cisco has directly contacted customers who own Cisco Secure Email Cloud devices where indicators of possible compromise were identified,” the company wrote in its security advisory. “Cisco is engaged in remediation and recovery operations. Cisco has already deployed mitigations that are within Cisco’s management.”

The Cybersecurity and Infrastructure Security Agency added the zero-day, which affects cloud-based and on-premises instances of Cisco Secure Email Gateway, to its known exploited vulnerabilities catalog shortly after Cisco’s disclosure. 

The tight timeline between Cisco’s public advisory and patch guidance, and CISA’s quick addition to the KEV catalog indicates the vulnerability deserves immediate attention, McKee said. 

“The combination here is pretty ugly. No authentication is required, an attacker can reach the vulnerable code by sending an email through the appliance, successful exploitation can result in root-level command execution, and Cisco has observed exploitation in the wild,” he added.

Researchers at Rapid7 and VulnCheck said they don’t yet know how many organizations are impacted by active exploits, but they encouraged Cisco customers to patch and hunt for potential signs of compromise as soon as possible. 

Spencer McIntyre, director of exploit development at VulnCheck, told CyberScoop the exploit could allow an attacker to maintain access to the email gateway and monitor communications. “Stealing or silently snooping on email comms is a common tactic for state-sponsored and other threat actors conducting espionage operations,” he said. 

“It’s going to be worse for organizations that have the appliance deployed on-premises. In this case, the attacker could pivot internally,” McIntyre added. “If, however, organizations use a cloud instance, the compromised gateway is less likely to have significant access to internal organizational resources.”

Cisco released indicators of compromise to help customers hunt for attempted exploitation in their environments, but the company added that attackers could remove or hide those traces with the level of access granted via exploitation.

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Microsoft addressed 974 defects across its product suite, including two actively exploited zero-day vulnerabilities, in its monthly Patch Tuesday security program. 

The massive batch of patches, Microsoft’s largest ever, reflects a continuing trend for the vendor as it leans on artificial intelligence to discover more vulnerabilities at a faster rate. Yet, the recent period of record breaking vulnerability disclosures hasn’t resulted in a flood of actively exploited zero-days.

“AI-assisted vulnerability discovery shows no signs of slowing down,” Dustin Childs, head of threat awareness at Trend Micro’s Zero Day Initiative, wrote in a blog post Tuesday. “However, we have not seen a correlating spike in active exploits — yet.”

The vulnerabilities actively exploited prior to disclosure — CVE-2026-81963 affecting the Windows Update Stack and CVE-2026-85880 affecting Windows Advanced Local Procedure Call — both have CVSS ratings of 7.8 and allow attackers to escalate privileges. 

More than 1 in 10 defects Microsoft disclosed in this month’s security update are rated critical. The update included 723 vulnerabilities in Windows, 111 in Office, 111 in Office 2016, 62 in SQL and 22 spanning various developer tools.

Researchers encouraged security teams and customers to not get overwhelmed by the total number of defects, but instead focus on their specific areas of risk and exposure. 

“While the number of vulnerabilities being patched is rising, the number of vulnerabilities that can and will affect most organizations remains quite low. AI-assisted vulnerability discovery in 2026 is creating larger haystacks, but it isn’t finding more needles,” Satnam Narang, senior staff research engineer at Tenable, said in an email. 

“It’s critical that organizations understand which vulnerabilities actually apply to them, whether they pose a threat by being reachable and exploitable, and prioritize remediation based on this risk context,” he added. 

Jack Bicer, director of vulnerability research at Action1, drew a similar conclusion from the record-breaking Patch Tuesday. 

“At this scale, the challenge is not simply getting through the patch list but knowing what needs attention first,” he said. “With hundreds of updates landing at once, IT and security teams need to quickly separate the vulnerabilities that demand immediate action from those that can follow the normal deployment cycle.”

The full list of vulnerabilities addressed this month is available in Microsoft’s Security Response Center.

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SonicWall customers are attempting to dodge another security challenge as attackers are exploiting a pair of zero-day vulnerabilities that have been confirmed by the vendor. 

The company publicly disclosed the vulnerabilities — CVE-2026-15409 and CVE-2026-15410 — in a security advisory Tuesday. SonicWall credited an employee with discovering the defects, but it hasn’t said when the discovery occurred or the earliest known instance of exploitation. 

Rapid7 researchers told CyberScoop both vulnerabilities were first exploited June 22. “From the cases that our team has observed, the goal is likely ransomware, though we have prevented the actors from achieving exfiltration and encryption,” said Seth Lazarus, senior manager of detection and response services at Rapid7.

Overlapping tactics, techniques and procedures from the attacks observed by Rapid7 indicate the same threat group or attacker discovered and exploited the zero-days, Lazarus added.

SonicWall did not answer questions about the impacts of these attacks thus far, and the company hasn’t attributed the attacks to a known group or described the attacker’s origins and motivations.

The vendor did, however, confirm to CyberScoop that both vulnerabilities have been chained together for exploitation. The vulnerabilities affecting SonicWall SMA1000 appliances, including a max-severity defect that allows attackers to make authenticated requests and a 7.2-rated vulnerability that allows authenticated command injection.

“When these two are chained, an attacker can go from zero access to a complete system compromise for the affected appliance,” said Landon Rice, senior exploit developer at VulnCheck.

Ben Harris, founder and CEO at watchTowr, said two characteristics of the vulnerabilities fuel a sense of dread. “Both were exploited as zero-days before fixes were available, and together they offer a plausible path to remote-code execution from the internet,” he said.

The Cybersecurity and Infrastructure Security Agency added both zero-days to its known exploited vulnerabilities catalog Tuesday. 

SonicWall encouraged customers to patch the vulnerabilities by upgrading to the latest software version, which it released upon disclosure, and shared some indicators of compromise to help customers hunt for potential malicious activity on their systems.

“Speed of response was a priority for us,” said Bret Fitzgerald, senior director of global communications at SonicWall. “Within days of becoming aware of the issue, our team had developed a script that we can run on behalf of affected customers to assist with resolution, and mitigation efforts are already underway.”

SonicWall and third-party researchers haven’t said how many SonicWall customers are impacted by the exploited vulnerabilities, but the vendor did say it already investigated multiple cases of active exploitation. 

Fitzgerald said the company monitors about one million sensors globally and “SMA1000 appliances represent a very small subset of that footprint, less than 5,000 units.”

SonicWall said support staff are also helping customers work through instances of suspicious activity, warning that patching alone is not sufficient. 

The vendor and its customers have been hit by a barrage of actively exploited zero-days and previously disclosed defects in SonicWall devices for years. In 2025, an undisclosed state-sponsored threat actor intruded the company’s cloud environment and stole firewall configurations of every SonicWall customer. 

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.

“As always,” Harris said, “when something is confirmed as already exploited in the wild, patching is the bare minimum, and breach should be assumed.”

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Microsoft’s monthly Patch Tuesday security program reached an unrivaled pinnacle this month, as the vendor addressed 622 vulnerabilities across its suite of business products and systems. 

“The bug apocalypse has finally descended upon us,” Dustin Childs, head of threat awareness at Trend Micro’s Zero Day Initiative, wrote in a blog post Tuesday.

“The mother of all releases. To call this record-breaking is an understatement,” he added. “The CVE count year-to-date exceeds all other years’ totals.”

The startling increase in vulnerabilities reflects a compounding effect taking root across software as artificial intelligence plays a growing role in discovering and developing patches for defects lurking in error-riddled applications. 

Microsoft’s June Patch Tuesday update broke the previous all-time record with 206 vulnerabilities.

The company last week warned forewarned customers and defenders that a flood of defects would be uncovered as it applies its multi-model agentic scanning harness (MDASH) to discover and address vulnerabilities at greater speed and scale.

The monthly exponential rise in Microsoft vulnerabilities already puts the vendor on pace to break a full-year record, ending 2026 with the largest annual collection of defects, beating the previous record of 1,245 CVEs in 2020, Satnam Narang, senior staff research engineer at Tenable, said in an email. 

“It’s probable that we will not only exceed 2,000 CVEs in a calendar year, but potentially over 3,000 CVEs this year or more,” he added.

“The volume is striking, but it reflects how good these tools have become at finding bugs, not how many of those bugs actually pose a risk to organizations,” Narang said.

Microsoft disclosed two actively exploited zero-day vulnerabilities — CVE-2026-56155 and CVE-2026-56164, privilege escalation defects in Active Directory Federation Services and Microsoft SharePoint Server, respectively. 

The monthly batch of patches included 416 defects in Windows, 82 in Office and 46 in Microsoft Edge. More than 1 in 10 vulnerabilities the vendor disclosed — 63 total — were rated as critical.

“The products covered this month are also astonishing,” Childs said. “Just about everything you’ve ever heard of is getting patched.”

The full list of vulnerabilities addressed this month is available in Microsoft’s Security Response Center.

SAP also addressed a fresh assortment of vulnerabilities Tuesday, including critical defects CVE-2026-44747 in SAP NetWeaver Application Server and CVE-2026-27690 in SAP Approuter.

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A major credential leak spurred the Cybersecurity and Infrastructure Security Agency to strengthen protections for its sensitive materials, improve how researchers can report agency vulnerabilities and develop plans for similar incidents, the agency said in a forensic report released Thursday.

The blog post outlines CISA’s response to the leak that the researcher who discovered it in May called one of the worst he had ever seen, which also drew congressional scrutiny.

“Sharing experiences from incident response activities help other organizations learn from such experiences and enables them to take necessary precautions to prevent similar incidents from happening in their environments,” wrote Preston Werntz, acting chief information officer and Brad Libbey, acting chief information security officer. “For years, CISA has said this type of information exchange is critical to identifying trends and contributing to broader national awareness. Now, it is our turn.”

On May 15, after learning about a contractor’s leak of privileged Amazon AWS GovCloud Keys on a public GitHub repository, CISA said it took steps to halt further harm. That meant taking the repository and its developer environment offline, and revoking the access of the person responsible for the leak.

CISA then analyzed the repository to get a sense of the scope of the leak. It also analyzed log files to learn that none of the leaked credentials were used outside of CISA, and that no customer or mission data was exposed.

The response benefited from taking the reported incident seriously, having good logging capabilities and using zero-trust principles, the blog post states.

But it also showed some things that needed to be fixed. 

CISA resolved to use its endpoint detection and response capabilities to monitor and manage uploads to public repositories. It rotated all of its secrets after the incident, and came up with a plan to improve management of its secrets.

It determined that it would make it easy to report vulnerabilities related to CISA itself. It’s better at receiving information about vulnerabilities that are less agency-specific, given its role as a hub of communication about cyber risks for the United States and world generally, the post noted.

CISA also said it had to build a playbook for GitHub-related incidents mid-incident, and recognized the need to build playbooks for all kinds of incidents in advance.

The person who uncovered the leak, GitGuardian security researcher Guillaume Valadon, applauded CISA’s evaluation of the incident. 

“I think that it is really good. CISA managed to explain what happened, what worked well and what needs to be improved,” he told CyberScoop via email. “This last part is, to me, the first time that a national cybersecurity agency is advocating for secrets scanning, and simplifying relations with researchers.” 

That’s something Valadon and his team have talked about for a while, and he said he was “proud to read that it is recognized by CISA.”

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