cisco-sa-esa-smime-disc-dzw4rEdYMediumCVSS 5.9

Cisco Secure Email Secure/Multipurpose Internet Mail Extensions Ciphertext Decryption Vulnerabilities

Published
September 2, 2026
Last Modified
September 8, 2026

🔗 CVE IDs covered (2)

CVE-2026-20354 →CVE-2026-20355 →

📋 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.

There are no workarounds that address these vulnerabilities.

CVE-2026-20354 — Cisco Secure Email S/MIME Ciphertext Decryption Vulnerabilty (CVSS 3.1 5.9, CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N) CVE-2026-20355 — Cisco Secure Email S/MIME Ciphertext Decryption Vulnerabilty (CVSS 3.1 5.9, CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N)

🎯 Affected products26

  • Cisco Secure Email
  • Cisco Secure Email 13.0.0-392
  • Cisco Secure Email 13.0.5-007
  • Cisco Secure Email 13.5.1-277
  • Cisco Secure Email 13.5.4-038
  • Cisco Secure Email 14.0.0-698
  • Cisco Secure Email 14.2.0-620
  • Cisco Secure Email 14.2.1-020
  • Cisco Secure Email 14.3.0-032
  • Cisco Secure Email 15.0.0-104
  • Cisco Secure Email 15.0.1-030
  • Cisco Secure Email 15.0.3-002
  • Cisco Secure Email 15.0.5-016
  • Cisco Secure Email 15.5.0-048
  • Cisco Secure Email 15.5.1-055
  • Cisco Secure Email 15.5.2-018
  • Cisco Secure Email 15.5.3-022
  • Cisco Secure Email 15.5.4-012
  • Cisco Secure Email 15.5.5-014
  • Cisco Secure Email 16.0.0-050
  • Cisco Secure Email 16.0.0-054
  • Cisco Secure Email 16.0.1-017
  • Cisco Secure Email 16.0.2-112
  • Cisco Secure Email 16.0.3-044
  • Cisco Secure Email 16.0.4-016
  • Cisco Secure Email 16.5.0-780

✅ Remediation

Cisco has released software updates that address this vulnerability. https://software.cisco.com Workarounds: There are no workarounds that address these vulnerabilities.

🔗 References (2)