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

In short

Cisco Multiple Products has a weakness classified as improper input validation (CWE-20). CISA added it to its Known Exploited Vulnerabilities catalog on 2025-12-17. NVD lists CVSS 3.1 at 10 CRITICAL.

What it is

“Cisco Secure Email Gateway, Secure Email, AsyncOS Software, and Web Manager appliances contains an improper input validation vulnerability that allows threat actors to execute arbitrary commands with root privileges on the underlying operating system of an affected appliance.” — CISA KEV, retrieved 2026-11-01

“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.” — NVD, retrieved 2026-11-01

Who is affected

Cisco Multiple Products. NVD lists the following versions as affected:

• Versions before 15.0.5-016
• Versions from 15.5 inclusive, before 15.5.4-012
• Versions from 16.0 inclusive, before 16.0.4-016
• Versions before 15.0.2-007
• Versions from 15.5 inclusive, before 15.5.4-007
• Versions from 16.0 inclusive, before 16.0.4-010

Exploitation status

CISA KEV added: 2025-12-17. Known ransomware campaign use: Not reported by CISA. Due date CISA set for US federal civilian agencies: 2025-12-24.

Scores

NVD CVSS 3.1: 10 CRITICAL; vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H; source [email protected].

EPSS by FIRST: 32.39%; percentile 98.33; score date 2026-10-31. EPSS estimates the probability of exploitation in the next 30 days.

CWE: CWE-20.

Timeline

CISA required action

“Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.” — CISA KEV

What to do

• Confirm whether you run Cisco Multiple Products and which version.
• Apply the vendor update or mitigation in the advisory.
• Follow CISA’s required action.
• Review the vendor guidance on signs of compromise.
• Track the fix through completion.

References

• Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sma-attack-N9bf4
• NVD detail
• CVE.org record
• CISA KEV catalog

Sources and dates

CISA Known Exploited Vulnerabilities Catalog, version 2026.10.30; retrieved 2026-11-01. CISA KEV data: CC0 1.0. No endorsement by CISA.

NVD retrieved: 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.

EPSS scores by FIRST; score date 2026-10-31.