CVE-2026-54876

A flaw was found in OpenSSL. A malicious TLS (Transport Layer Security) server can exploit this vulnerability by sending a specially crafted OCSP (Online Certificate Status Protocol) response during the X.509 certificate chain verification process. This can lead to a memory leak in client applications that have enabled OCSP response checking. Repeated connections to a malicious server could exhaust the client's memory, ultimately resulting in a Denial of Service (DoS).

This vulnerability is rated Important because a malicious TLS server can cause memory exhaustion and denial of service in a long-running client. Exploitation requires the client application to enable OCSP response checking and process a crafted OCSP response from the server. Exposure therefore depends on the application’s configuration.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

No broadly applicable mitigation is available. If an affected client application provides a configuration setting for OCSP response checking, operators can temporarily disable it where their certificate revocation policy permits. This blocks the vulnerable response-checking path but removes OCSP-based revocation checks. Clients that must keep OCSP response checking enabled remain exposed.