SB2026090284 - Multiple vulnerabilities in Cisco Secure Email Gateway

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Main Vulnerability Database SB2026090284

SB2026090284 - Multiple vulnerabilities in Cisco Secure Email Gateway

Published: September 2, 2026

Security Bulletin ID SB2026090284
CSH Severity
Medium
Patch available
YES
Number of vulnerabilities 2
Exploitation vector Remote access
Highest impact Information disclosure

Breakdown by Severity

Medium 100%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 2 vulnerabilities.


1) Insufficient verification of data authenticity (CVE-ID: CVE-2026-20354)

CWE-ID: CWE-345 - Insufficient Verification of Data Authenticity

CVSSv4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]


The vulnerability allows a remote attacker to disclose sensitive information.

The vulnerability exists due to insufficient validation of message integrity in the S/MIME decryption functionality when processing intercepted and modified traffic between email gateways. A remote attacker can use a machine-in-the-middle technique to intercept and modify traffic to disclose sensitive information.

Only deployments with S/MIME configured for communication between email gateways are vulnerable.


2) Improper validation of integrity check value (CVE-ID: CVE-2026-20355)

CWE-ID: CWE-354 - Improper Validation of Integrity Check Value

CVSSv4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]


The vulnerability allows a remote attacker to disclose sensitive information.

The vulnerability exists due to insufficient validation of message integrity in the S/MIME decryption functionality when processing intercepted and modified traffic between email gateways. A remote attacker can use a machine-in-the-middle technique to intercept and modify traffic to disclose sensitive information.

Only deployments with S/MIME configured for communication between email gateways are vulnerable.


Remediation

Install update from vendor's website.

References