During the processing of a CMS EnvelopedData message that includes KeyAgreeRecipientInfo, OpenSSL may dereference a NULL pointer if the optional parameters field of the KeyEncryptionAlgorithmIdentifier is missing. This causes the application to crash before any authentication or cryptographic operations happen. The resulting denial of service can make systems that accept CMS data, such as S/MIME mail processing or other CMS‑based protocols, unavailable.

All OpenSSL deployments that use the CMS_decrypt routine to process attacker‑controlled CMS data are vulnerable. The issue is present in code outside the FIPS module, so the FIPS 3.x modules (3.6, 3.5, 3.4, 3.3, 3.0) are not affected. Systems that handle S/MIME, secure email, or other CMS‑based protocols could be impacted when they receive malformed CMS messages.

With a CVSS score of 7.5 the severity is moderate, but the EPSS score is below 1 % and the vulnerability is not listed in the CISA KEV catalog, indicating a low likelihood of widespread exploitation. An attacker would need to supply a crafted CMS EnvelopedData message containing KeyAgreeRecipientInfo without optional parameters. Successful exploitation would crash the application, leading to a denial of service. The attack vector is therefore likely remote over trusted channels where CMS data is accepted.