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CVE-2026-54876 is a client-side memory leak in OpenSSL OCSP response checking. The flaw is triggered during X.509 certificate chain verification when a TLS client has explicitly enabled OCSP response checking using the X509_V_FLAG_OCSP_RESP_CHECK or X509_V_FLAG_OCSP_RESP_CHECK_ALL verification flags and processes a stapled OCSP BasicOCSPResponse from a malicious server. If the BasicOCSPResponse contains an empty SEQUENCE OF SingleResponse entries, which is accepted by the OpenSSL decoder, an OCSP_BASICRESP structure allocated by OCSP_response_get1_basic() is not freed because an early return bypasses the normal cleanup path. The leaked allocation can be enlarged by including additional bogus certificates in the response so they are parsed and retained in the leaked structure before the empty-response condition is detected. The issue affects OpenSSL 4.0 and 3.6. OpenSSL 3.5, 3.4, 3.0, 1.1.1, and 1.0.2 are not affected. The OpenSSL FIPS modules in 4.0 and 3.6 are not affected because the vulnerable code is outside the FIPS module boundary.
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8 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A low-severity OpenSSL client-side memory leak in OCSP response checking that can allow a malicious TLS server to exhaust memory in long-running client applications, leading to denial of service.
A low-severity client-side memory leak in OpenSSL OCSP response checking that can let a malicious TLS server exhaust memory in long-running TLS clients when OCSP response checking is explicitly enabled.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.