OpenSSL NULL Pointer Dereference Vulnerability in CMP EncryptedValue Decryption

A NULL pointer dereference vulnerability has been identified in OpenSSL's CMP client application. This issue arises when the client processes a response from an attacker-controlled CMP server that includes a CRMF CertRepMessage with an EncryptedValue structure. If the symmAlg field contains an algorithm OID without accompanying parameters, the CMP client will dereference a NULL pointer, leading to a crash and causing a denial-of-service condition. This vulnerability affects OpenSSL versions 4.0, 3.6, 3.5, 3.4, and 3.0, but not the FIPS modules in these versions, as the issue occurs outside the FIPS module boundary.

Impact

Exploitation of this vulnerability causes a crash of the CMP client application, leading to a denial-of-service condition.

Reproduction

To reproduce this vulnerability, an attacker must control a CMP server and send a response to a CMP client that includes a CRMF CertRepMessage. The EncryptedValue structure must be crafted so that the symmAlg field contains an algorithm OID but no parameters. When the OpenSSL CMP client processes this response, the NULL pointer dereference occurs, causing the application to crash.

Remediation

Users of OpenSSL 4.0 should upgrade to OpenSSL 4.0.1. Users of OpenSSL 3.6 should upgrade to OpenSSL 3.6.3. Users of OpenSSL 3.5 should upgrade to OpenSSL 3.5.7. Users of OpenSSL 3.4 should upgrade to OpenSSL 3.4.6. Users of OpenSSL 3.0 should upgrade to OpenSSL 3.0.21.