CVE-2026-34182

Name of the Vulnerable Software and Affected Versions OpenSSL (affected versions not specified)

Description Cryptographic Message Services (CMS) processing fails to perform sufficient input validation on the cipher and tag length fields of AuthEnvelopedData containers. This allows attackers to achieve key-equivalent functionality for a CMS recipient or bypass integrity validation for a message. In one scenario, an attacker can send a CMS message where the cipher is specified as a non-AEAD (Authenticated Encryption with Associated Data) cipher. If an attacker captures a legitimate AES-GCM AuthEnvelopedData message, they can rewrite the inner OID to AES-256-OFB (an unauthenticated keystream mode) with a chosen IV and ciphertext. If the application provides feedback on the success or failure of the decryption, it can act as an oracle to obtain key-equivalent functionality for the CEK (content-encryption key). Additionally, an attacker can reduce the tag length of an AEAD cipher to a single byte, enabling a brute-force attack to bypass integrity checks in applications relying on the CMS decrypt() function to reject modified content.

Recommendations At the moment, there is no information about a newer version that contains a fix for this vulnerability.