Secure Email and Web
CVE-2025-20153: Cisco ESA mail Bypass
A vulnerability in the email filtering mechanism of Cisco Secure Email Gateway could allow an unauthenticated, remote attacker to bypass the configured rules and allow emails that should have been denied to flow through an affected device.
Published
Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.
Affected and fixed versions
| Product / branch | Fixed in |
|---|---|
| Cisco Secure Email 14.0 | See the advisory |
| Cisco Secure Email 13.5 | See the advisory |
| Cisco Secure Email 13.0 | See the advisory |
| Cisco Secure Email 14.2 | See the advisory |
| Cisco Secure Email 13.0 | See the advisory |
| Cisco Secure Email 13.5 | See the advisory |
| Cisco Secure Email 14.2 | See the advisory |
| Cisco Secure Email 14.3 | See the advisory |
| Cisco Secure Email 15.0 | See the advisory |
| Cisco Secure Email 15.0 | See the advisory |
| Cisco Secure Email 15.5 | See the advisory |
| Cisco Secure Email 15.5 | See the advisory |
| Cisco Secure Email 15.5 | See the advisory |
| Cisco Secure Email 16.0 | See the advisory |
| Cisco Secure Email 15.0 | See the advisory |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
A vulnerability in the email filtering mechanism of Cisco Secure Email Gateway could allow an unauthenticated, remote attacker to bypass the configured rules and allow emails that should have been denied to flow through an affected device.
This vulnerability is due to improper handling of email that passes through an affected device. An attacker could exploit this vulnerability by sending a crafted email through the affected device. A successful exploit could allow the attacker to bypass email filters on the affected device.
Exploitation
The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
Sources
KEV status, EPSS score and vendor data refreshed automatically, last on 11 Oct 2026.