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TI-2026-16538 Aliases CVE-2026-20355GHSA-4rjc-g85j-x387

Cisco Secure Email S/MIME Ciphertext Decryption Vulnerabilty

Priority LOW 26CWE-345Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
Security bypass
Confidentiality · integrity · availability
High · None · None
Fix status
No fix listed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-345.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00203 10th percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
CiscoCisco Secure Email14.0.0-698; 13.5.1-277; 13.0.0-392; 14.2.0-620; 13.0.5-007; 13.5.4-038; 14.2.1-020; 14.3.0-032; 15.0.0-104; 15.0.1-030; 15.5.0-048; 15.5.1-055; 15.5.2-018; 16.0.0-050; 15.0.3-002; 16.0.0-054; 15.5.3-022; 16.0.1-017; 15.5.4-012; 16.0.4-016; 15.0.5-016; 16.0.2-112; 16.0.3-044; 16.5.0-780—No fix listedCNA
  • Cisco Secure Email VendorCisco Affected 14.0.0-698; 13.5.1-277; 13.0.0-392; 14.2.0-620; 13.0.5-007; 13.5.4-038; 14.2.1-020; 14.3.0-032; 15.0.0-104; 15.0.1-030; 15.5.0-048; 15.5.1-055; 15.5.2-018; 16.0.0-050; 15.0.3-002; 16.0.0-054; 15.5.3-022; 16.0.1-017; 15.5.4-012; 16.0.4-016; 15.0.5-016; 16.0.2-112; 16.0.3-044; 16.5.0-780 Fixed in — No fix listed CNA

Remediation

No fixed version listed by the sources yet.

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-20355
  2. 2026-10-03 Alias added: GHSA-4rjc-g85j-x387

References

Other 1

  • TI-2026-74174 Arbitrary file write in Cisco Secure Email Gateway via AMP feature KEVCVSS 3.1CRITICAL 9.8
  • TI-2026-53490 Cisco Catalyst SD-WAN Manager System Account Authorization Bypass Vulnerability KEVCVSS 3.1CRITICAL 9.8
  • TI-2026-53489 Cisco Secure Email Gateway SQL Injection Vulnerability KEVCVSS 3.1CRITICAL 9.8
  • TI-2026-53488 Cisco Identity Services Engine Authentication Bypass Vulnerability KEVCVSS 3.1CRITICAL 10.0
  • TI-2026-16388 Cisco Catalyst SD-WAN Controller Authentication Bypass Vulnerability KEVCVSS 3.1CRITICAL 10.0
  • TI-2026-16344 Cisco Secure Firewall Management Center Software Remote Code Execution Vulnerability KEVCVSS 3.1CRITICAL 10.0
See all 7059 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences