CVE-2026-35189

A certificate containing a large number of nameRelativeToCRLIssuer CRL distribution points can trigger disproportionate heap growth when OpenSSL caches X.509 extensions during a TLS handshake. This excessive allocation can consume hundreds of megabytes of resident memory, potentially causing the client or server process to crash or become unresponsive. The vulnerability is a CWE‑770: Allocation of Resources Without Limits or Throttling, leading to a denial of service condition.

The issue impacts OpenSSL libraries that process client certificates. All installations of OpenSSL that perform normal TLS handshakes and cache X.509 extensions are potentially affected. No specific version range is listed, so any version prior to the fix in the referenced commits is vulnerable. The affected code resides outside the FIPS module boundary, so it applies to general OpenSSL usage.

Attackers can exploit the vulnerability by presenting a crafted certificate containing many CRL distribution points during a TLS handshake with a server that accepts client certificates. The exploit does not require privileged access or code execution; it merely sends the certificate, consuming memory on the remote side. The CVSS score of 5.3 indicates a medium severity, while the EPSS score of 0.00118 (less than 1%) suggests a very low but non-zero likelihood of exploitation, and the vulnerability is not listed in CISA KEV; nevertheless, the potential for memory exhaustion and service interruption makes it a high operational risk.