Vulnerability in Cisco Secure Email
CVE-2026-20355
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.002 (4.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 5th percentile — 4.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.001 · newest: 0.002 · change: +0.000
Affected products
- Cisco Secure Email — versions 13.0.0-392, 13.0.5-007, 13.5.1-277
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-20355?
- CVE-2026-20355 is a medium-severity vulnerability in Cisco Secure Email, classified under Insufficient Verification of Data Authenticity. CVSS score: 5.9/10. Published 2026-09-02.
- How severe is CVE-2026-20355?
- Medium severity. CVSS v3 base score is 5.9 out of 10.