CVE-2026-20354 MEDIUM

CVE-2026-20354: Cisco Secure Email S/MIME Ciphertext Decryption Vulnerabilty

Vendor Cisco
Product Cisco Secure Email
Weakness CWE-354
Published September 2, 2026
Last update September 2, 2026

CVSS base score

5.9/10
Attack vector Network
Attack complexity High
Privileges required None
User interaction None
Confidentiality High
Integrity None

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

September 2, 2026 CVE published
September 2, 2026 Record updated