CVE-2025-20393: Cisco Multiple Products

What is CVE-2025-20393?

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.

CVSS10 NVD 3.1

SeverityCRITICAL

Exploitation In the wild In CISA KEV

EPSS32% · P98

Triage statusActive Exploit

ActionPatch immediately

CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

CWECWE-20

NVD published2025-12-17

NVD last modified2026-06-17

Timeline

2025-12-17Published to the U.S. National Vulnerability Database (NVD)
2025-12-17Added to the CISA Known Exploited Vulnerabilities (KEV) catalog
2025-12-24CISA federal remediation deadline (BOD 22-01)
2026-06-17NVD record last updated
2026-10-15First covered in a defend.network daily briefing

CISA Known Exploited Vulnerability

Cisco Multiple Products Improper Input Validation Vulnerability

Added to KEV2025-12-17

Federal patch deadline2025-12-24

Known ransomware useUnknown

Affected product

Cisco Multiple Products

NVD also lists CPE entries for: Cisco Asyncos, Cisco Secure Email Gateway Virtual Appliance C100v, Cisco Secure Email Gateway Virtual Appliance C300v, Cisco Secure Email Gateway Virtual Appliance C600v, Cisco Secure Email Gateway C195

Remediation Steps

Apply the vendor security update for Cisco Secure Email Gateway as a priority.
Restrict network exposure of the affected service to trusted sources until patched.
Review logs and detections for indicators of exploitation.
Confirm fixed versions against the official vendor advisory before deploying.

References

Referenced in our briefings & reports

Vulnerability Priority Report – Week 2 of October 2026 (October 12 – 18)
Cisco Email Gateway RCE exploited; Nextcloud backdoors; 3 phishing platforms disrupted (2026-10-15)

Browse all tracked CVEs in the defend.network CVE database →

🤖 This CVE page is generated by defend.network from NVD, CISA KEV, EPSS, and our verified daily briefings. Severity and exploitation data come from official sources; always verify remediation steps against the official vendor advisory before acting in production.