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

• Severity: critical (CVSS 10.0 v3.1)
• Exploited in the wild: yes — in CISA KEV since 2025-12-17
• EPSS: 32.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-12-17 · updated 2026-06-17
• Weakness: CWE-20

Description

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; from 15.5 before 15.5.4-012; from 16.0 before 16.0.4-016; before 15.0.2-007; from 15.5 before 15.5.4-007; from 16.0 before 16.0.4-010 — fixed in 15.0.2-007, 15.0.5-016, 15.5.4-007, 15.5.4-012, 16.0.4-010, 16.0.4-016

How to fix

Upgrade to a fixed version: Cisco Asyncos 15.0.2-007, 15.0.5-016, 15.5.4-007, 15.5.4-012. Check the vendor advisory for mitigations.

References

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sma-attack-N9bf4
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-20393

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