CVE-2026-20355: Cisco Secure Email S/MIME Ciphertext Decryption Vulnerabilty
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.
Event History
Frequently Asked Questions
Who is exposed to exploitation?
Organizations using Cisco Secure Email S/MIME decryption are exposed when an attacker can position themselves between email gateways and intercept their traffic. The attacker does not need authentication or user interaction.
What does an attacker need to do to exploit this issue?
The attacker must perform a machine-in-the-middle attack against traffic between email gateways and modify intercepted encrypted messages. Exploitation depends on the integrity-validation weakness in S/MIME decryption.
What is the impact of a successful attack?
A successful attack can allow recovery of plaintext content from encrypted email communications. The provided severity data indicates confidentiality impact is high, with no stated integrity or availability impact.