CVE-2026-63076

Issue summary: OpenSSL CMP password based protection verification only<br /> checks whether the protectionAlg parameter was not NULL and not its<br /> ASN.1 type, before treating it as a PBMParameter. A crafted message can<br /> contain a parameter of a different type, which is then dereferenced as an<br /> invalid pointer.<br /> <br /> Impact summary: A remote, unauthenticated attacker can crash an application<br /> acting as a CMP server that accepts PBM-protected messages, or a CMP client<br /> talking to a malicious or intercepted CMP server, resulting in a Denial of<br /> Service.<br /> <br /> CWE: CWE-476: NULL Pointer Dereference<br /> <br /> Description: When verifying the password-based MAC protection of a CMP<br /> message, OpenSSL library reads the protectionAlg algorithm parameter with<br /> X509_ALGOR_get0(), which returns both the parameter type and its value<br /> pointer. The value is then cast to an ASN1_STRING and treated as the<br /> expected PBMParameter after only checking that pointer is not NULL. The<br /> parameter type returned by X509_ALGOR_get0() was never consulted.<br /> <br /> This happens during protection verification, before any MAC is computed, so<br /> no knowledge of the PBM shared secret is required; the only precondition is<br /> that PBM verification is reachable. On the server side this is reached from<br /> OSSL_CMP_SRV_process_request() for any application that stands up a CMP<br /> server accepting PBM-protected messages, and on the client side from CMP<br /> response validation against a malicious or on-path (MITM) server. The<br /> reliable consequence is a denial of service; there is no memory disclosure,<br /> no controlled memory write, and no path to code execution. CMP is a<br /> specialized feature that an application must explicitly enable.<br /> <br /> FIPS impact: no<br /> As the CMP code lives outside the FIPS module boundary, no FIPS modules<br /> are affected by this CVE.