NULL Pointer Dereference Vulnerability in OpenSSL's Certificate Verification

CVE-2026-28388

What is CVE-2026-28388?

A vulnerability exists in OpenSSL's handling of delta CRLs during X.509 certificate verification. When processing a delta CRL that lacks the required CRL Number extension, the system may attempt to dereference a NULL pointer. This can lead to application crashes and result in Denial of Service. The issue is primarily relevant when the X509_V_FLAG_USE_DELTAS flag is enabled, and a malformed CRL is supplied. It does not allow for code execution or memory disclosure.

References