CVE-2026-20355
Cisco Secure Email S/MIME Ciphertext Decryption Vulnerabilty
Severity
Medium 5.9
CVSS 3.1
Exploited
Not listed
EPSS
0.001
4.5th percentile
Discovered by
Third party
Vendor-published field
Published
Sep 2, 2026
Assigned by cisco
Description
Multiple vulnerabilities in the Secure/Multipurpose Internet Mail Extensions (S/MIME) decryption functionality of Cisco Secure Email could allow an unauthenticated, remote attacker to recover plain text from encrypted email messages. These vulnerabilities are due to insufficient validation of message integrity. An attacker could exploit these vulnerabilities by using a machine-in-the-middle technique to intercept and modify traffic between email gateways. A successful exploit could allow the attacker to obtain plaintext content from the encrypted communication.
Weakness: CWE-345
Affected products
| Vendor | Product | Category | Matched by |
|---|---|---|---|
| Cisco | Cisco Secure Email Gateway | Email Security | cna-assigner |
Vendor-reported products (1)
- Cisco · Cisco Secure Email