CVE-2026-20355Cisco Secure Email S/MIME Ciphertext Decryption Vulnerabilty
- 5.9MediumCVSS base score
- 0.20%Exploitation in 30 daysEPSS · top 90% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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.
Timeline
ID reserved
By cisco
- 11 months later
· 11 months later
Published
- 6 days later
· 6 days later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| ciscoCNA (assigner) | 3.1 | Medium5.9 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N |
| NVDNVD · Awaiting Analysis | 3.1 | Medium5.9 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N |
- EPSS (exploitation in 30 days)
- 0.20% · top 90% of all CVEs (14 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.9.
Affected products
- affected 14.0.0-698
- affected 13.5.1-277
- affected 13.0.0-392
- affected 14.2.0-620
- affected 13.0.5-007
- affected 13.5.4-038
- affected 14.2.1-020
- affected 14.3.0-032
- affected 15.0.0-104
- affected 15.0.1-030
- affected 15.5.0-048
- affected 15.5.1-055
- affected 15.5.2-018
- affected 16.0.0-050
- affected 15.0.3-002
- affected 16.0.0-054
- affected 15.5.3-022
- affected 16.0.1-017
- affected 15.5.4-012
- affected 16.0.4-016
- affected 15.0.5-016
- affected 16.0.2-112
- affected 16.0.3-044
- affected 16.5.0-780
What to do
Exploitation: The Cisco Product Security Incident Response Team (PSIRT) is aware that a public announcement is available for the vulnerabilities that are described in this advisory. The Cisco PSIRT is not aware of any malicious use of the vulnerabilities that are described in this advisory.
References
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-70211 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-20355)Record last updated .