A crafted CMS EnvelopedData message that uses KeyTransportRecipientInfo with RSA‑OAEP can trigger a NULL pointer dereference when the optional parameters field of the RSA‑OAEP algorithm identifier is missing and examined without a null check. The failure occurs before authentication or cryptographic operations, leading to a crash of the application and a denial‑of‑service condition. The weakness is a classic NULL pointer dereference (CWE‑476).

The flaw resides in the CMS implementation of the OpenSSL library for all non‑FIPS builds. Any program that processes CMS data via CMS_decrypt(), such as S/MIME handlers or other CMS‑based protocols, is potentially vulnerable. The FIPS modules (3.6, 3.5, 3.4, 3.3 and 3.0) are unaffected because the vulnerable code lies outside the FIPS boundary.

The CVSS score of 7.5 reflects a high‑severity impact, yet the EPSS score is below 1 % and the issue is not listed in CISA’s KEV catalog, suggesting low current exploitation activity. An attacker would need to supply a malicious CMS EnvelopedData message to a vulnerable application; a successful exploit would cause an application crash and downtime. Proper input validation or disallowing the processing of KeyTransportRecipientInfo from untrusted sources mitigates the risk, but the most reliable defense is applying the vendor patch.