Cisco warns of unpatched AsyncOS zero-day exploited in attacks

BleepingComputer

December 17, 2025 at 6:45 PM

Actively Exploited

Overview

Cisco has issued a warning regarding a serious zero-day vulnerability in its AsyncOS software that is currently being exploited in the wild. This flaw affects Cisco's Secure Email Gateway (SEG) and Secure Email and Web Manager (SEWM) appliances, leaving customers vulnerable to potential attacks. The zero-day has been classified with maximum severity, indicating the urgency for organizations using these products to take action. As of now, there are no patches available to address this vulnerability, which raises concerns about the security of email communications for affected users. Companies that rely on these Cisco products should closely monitor their systems and implement any available security measures to mitigate risks until a fix is released.

Key Takeaways

Active Exploitation: This vulnerability is being actively exploited by attackers. Immediate action is recommended.
Affected Systems: Cisco Secure Email Gateway (SEG), Cisco Secure Email and Web Manager (SEWM)
Action Required: Organizations should monitor their systems for suspicious activity and consider implementing additional security measures, such as intrusion detection systems or enhanced email filtering, to help mitigate risks until a patch is available.
Timeline: Newly disclosed

Original Article Summary

Cisco warned customers today of an unpatched, maximum-severity Cisco AsyncOS zero-day actively exploited in attacks targeting Secure Email Gateway (SEG) and Secure Email and Web Manager (SEWM) appliances. [...]

Impact

Cisco Secure Email Gateway (SEG), Cisco Secure Email and Web Manager (SEWM)

Exploitation Status

This vulnerability is confirmed to be actively exploited by attackers in real-world attacks. Organizations should prioritize patching or implementing workarounds immediately.

Timeline

Newly disclosed

Remediation

Organizations should monitor their systems for suspicious activity and consider implementing additional security measures, such as intrusion detection systems or enhanced email filtering, to help mitigate risks until a patch is available.

Additional Information

This threat intelligence is aggregated from trusted cybersecurity sources. For the most up-to-date information, technical details, and official vendor guidance, please refer to the original article linked below.

Related Topics: This incident relates to Zero-day, Cisco, Vulnerability.

Read Original Article

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