CVE-2025-20393: Cisco Multiple Products Improper Input Validation Vulnerability

Critical severity, CVSS 10.0. Actively exploited: in CISA KEV since 2025-12-17. EPSS: 32.4% chance of exploitation in the next 30 days.

A vulnerability in the Spam Quarantine feature of Cisco AsyncOS Software for Cisco Secure Email Gateway and Cisco Secure Email and Web Manager could allow an unauthenticated, remote attacker to execute arbitrary system commands on an affected device with root privileges. This vulnerability is due to insufficient validation of HTTP requests by the Spam Quarantine feature. An attacker could exploit this vulnerability by sending a crafted HTTP request to the affected device. A successful exploit could allow the attacker to execute arbitrary commands on the underlying operating system with root privileges.

Affected products

• Cisco Asyncos: before 15.0.5-016 (fixed in 15.0.5-016); from 15.5, before 15.5.4-012 (fixed in 15.5.4-012); from 16.0, before 16.0.4-016 (fixed in 16.0.4-016); before 15.0.2-007 (fixed in 15.0.2-007); from 15.5, before 15.5.4-007 (fixed in 15.5.4-007); from 16.0, before 16.0.4-010 (fixed in 16.0.4-010)

Published 2025-12-17. Last modified 2026-06-17.