CVE-2026-34182

/// Technical description

Issue Summary: Cryptographic Message Services (CMS) processing fails to perform

sufficient input validation on the cipher and tag length fields of

AuthEnvelopedData containers, leading to various potential compromises.

Impact Summary: Attackers making use of these vulnerabilities may achieve

key-equivalent functionality for a given CMS recipient and/or bypass integrity

validation for a given message.

In one use case, an attacker may send a CMS message containing

AuthEnvelopedData with the cipher specified as a non-AEAD cipher. OpenSSL

erroneously allows this selection, and attempts to decrypt and validate the

message.

An on-path attacker who captures one legitimate AES-GCM AuthEnvelopedData

addressed to the victim can re-emit it with the recipientInfos set left

byte-for-byte intact, so the victim's private key still unwraps the genuine CEK

(the content-encryption key), but with the inner OID rewritten to AES-256-OFB

(Output Feedback Mode, an unauthenticated keystream mode) and with

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References