CVE-2025-20393: Cisco Secure Email Gateway command injection in Spam Quarantine

CVE-2025-20393 · Severity: critical · CVSS 10 · Exploited in the wild · Published 2025-12-17

Cisco email and web security appliances are affected by a critical vulnerability that allows unauthorized individuals to take full control of the device. These appliances are used to filter malicious emails and manage web traffic for corporate networks. An attacker could exploit this to disrupt communications, steal sensitive data, or use the device as a foothold to attack other parts of the internal network.

Technologies: Apple Multiple Products, Cisco Secure Email and Web Manager, Cisco Secure Email Gateway. Vendors: Apple, Cisco.

Quick answers

Is CVE-2025-20393 exploited in the wild?
Yes. CVE-2025-20393 is known to be exploited in the wild, first recorded on 17 December 2025. Treat it as urgent.
How severe is CVE-2025-20393?
Critical severity, with a CVSS score of 10, published 17 December 2025.
Which products and versions are affected?
Cisco Secure Email and Web Manager AsyncOS < 15.0.5-016, 15.5.x < 15.5.4-012, 16.0.x < 16.0.4-016; Cisco Secure Email Gateway AsyncOS < 15.0.5-016, 15.5.x < 15.5.4-012, 16.0.x < 16.0.4-016.
Is there a fix for CVE-2025-20393?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2025-20393 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2025-20393?
Check whether you run Apple Multiple Products, Cisco Secure Email and Web Manager or Cisco Secure Email Gateway at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

An improper input validation vulnerability exists in the Spam Quarantine feature of Cisco AsyncOS Software. The flaw is triggered by insufficient validation of incoming HTTP requests, allowing a remote, unauthenticated attacker to inject and execute arbitrary system commands. By sending a specially crafted HTTP request to the affected device, an attacker can gain full root-level access to the underlying operating system. This vulnerability has been observed being exploited in the wild. Cisco has released software updates to address this issue across affected AsyncOS versions.

Affected products

  • Cisco Secure Email Gateway AsyncOS < 15.0.5-016, 15.5.x < 15.5.4-012, 16.0.x < 16.0.4-016
  • Cisco Secure Email and Web Manager AsyncOS < 15.0.5-016, 15.5.x < 15.5.4-012, 16.0.x < 16.0.4-016

Timeline

  • 2025-12-17: advisory: Initial Cisco advisory and NVD publication
  • 2025-12-17: kev added: Added to CISA Known Exploited Vulnerabilities catalog
  • 2025-12-17: exploited: Confirmed active exploitation in the wild

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