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 for 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.