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🚨Cisco SEG Vulnerability Allows Root Access via Email Attachments

Critical Cisco SEG Bug Exploited Before Fix

TL;DR

A critical vulnerability in Cisco's Secure Email Gateway (SEG) allows attackers to gain root access via email attachments. The bug, tracked as CVE-2026-76519, was exploited before Cisco issued a fix. Federal agencies have a Saturday deadline to patch.

Cisco's Secure Email Gateway (SEG) is facing a critical vulnerability that allows attackers to gain root access by sending malicious email attachments. The bug, tracked as CVE-2026-76519, received a CVSS score of 9.8 and was exploited in zero-day attacks before a fix was issued. This vulnerability affects a limited number of customers and impacts both physical and virtual SEG appliances running AsyncOS Software versions earlier than 16.5.0-780. The flaw exists in the Advanced Malware Protection (AMP) feature and requires the File Reputation service to be enabled and assigned to a mail policy. Upgrading to a fixed Cisco AsyncOS Software release is the only solution. This is the second such zero-day in SEG in as many months.

Cisco SEG Vulnerability Allows Root Access via Email Attachments — theregister

Key Points

1

CVE-2026-76519 allows attackers to write files and execute commands with root privileges on SEG appliances.

2

The vulnerability affects both physical and virtual SEG appliances running AsyncOS Software earlier than v16.5.0-780.

3

File Reputation service must be enabled and assigned to a mail policy for the vulnerability to be exploitable.

4

Cisco recommends upgrading to AsyncOS Software v16.5.0-780 to patch the security hole.

5

US CISA added the vulnerability to its Known Exploited Vulnerabilities catalog.

Why It Matters

If you're running Cisco SEG with AsyncOS Software earlier than v16.5.0-780, you're at risk. The vulnerability allows attackers to gain root access via email attachments, potentially leading to data breaches and system compromises. Upgrading to the latest version is crucial to mitigate this risk.

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