Cisco alerts customers to second actively exploited zero-day in as many days

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Cisco disclosed its second actively exploited zero-day vulnerability in as many days, presenting its customers with back-to-back threats to address in unrelated products.

The latest zero-day — CVE-2026-76460 — has a maximum-severity rating and was exploited before Cisco disclosed and patched the vulnerability Wednesday. The defect in an API of Cisco Identity Services Engine (ISE) allows a remote attacker to bypass authentication and gain full control of the affected device.

“ISE devices enforce network access policy, so root access on the appliance lets an attacker modify that policy, extract stored credentials, delete logs, and move laterally into every network segment ISE controls,” Landon Rice, senior exploit developer at VulnCheck, told CyberScoop.

Cisco did not say how many organizations have been compromised thus far, but reported it found the vulnerability during a technical support case. 

“Cisco is aware of active exploitation of this vulnerability. We strongly recommend customers upgrade to available fixed software and follow guidance in the advisory,” a Cisco spokesperson said in a statement.

The Cybersecurity and Infrastructure Security Agency added the zero-day to its known exploited vulnerabilities catalog shortly after Cisco’s disclosure. 

Researchers haven’t attributed attacks involving CVE-2026-76460 to any known group or threat actor, but Rice noted Cisco ISE vulnerabilities are a recurring target. 

Multiple vulnerabilities affecting the Cisco product have been exploited since June 2025, including CVE-2025-20337 and CVE-2025-20281. The latest zero-day vulnerability and the pair of defects disclosed in the summer of 2025 were all rated critical with the highest rating of 10. 

Cisco didn’t say when the first instance of CVE-2026-76460 exploitation occurred, but the disclosure came just two days after the vendor disclosed CVE-2026-76461, an actively exploited zero-day vulnerability in Cisco Secure Email Gateway. 

While the two zero-days disclosed this week have consecutive CVE identifiers, there’s no indication they are connected or share any technical relationship, Rice said. “These are different products and different vulnerability classes with no relation,” he added.

A Cisco spokesperson concurred with that assessment. “CVEs are assigned on a first-come, first-served basis, so consecutive numbering reflects assignment order rather than any relationship between the issues. CVE-2026-76460 and CVE-2026-76461 affect different codebases,” the spokesperson added.

Cisco published indicators of compromise to help customers hunt for attempted exploitation in their environments, and said there are no workarounds for the vulnerability.

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