Source: openssl Version: 3.6.3-1 Severity: important Tags: security upstream X-Debbugs-Cc: [email protected], Debian Security Team <[email protected]>
Hi, The following vulnerability was published for openssl. CVE-2026-54876[0]: | Issue summary: A malicious TLS server can cause a memory leak in a | TLS client that has enabled OCSP response checking by sending an | OCSP response that contains no single response entries. Impact | summary: An attacker can leak an attacker-tunable amount of memory | per TLS handshake in a victim client application. A long-running | client that repeatedly connects to a malicious server can have its | memory exhausted, resulting in a Denial of Service. CWE: CWE-401: | Missing Release of Memory after Effective Lifetime Description: The | affected function is called during X.509 certificate chain | verification when OCSP response checking is enabled with the | X509_V_FLAG_OCSP_RESP_CHECK or X509_V_FLAG_OCSP_RESP_CHECK_ALL | verification flags, for example when a TLS client verifies an OCSP | response stapled into the TLS handshake by the server. When the | received BasicOCSPResponse contains an empty SEQUENCE OF | SingleResponse, which is permitted on the wire and accepted by the | OpenSSL decoder, the OCSP_BASICRESP structure allocated by | OCSP_response_get1_basic() was not freed because an early return | bypassed the cleanup code at the end of the function. The amount of | memory leaked per handshake can be amplified by the attacker by | padding the certs field of the BasicOCSPResponse with bogus | certificates, which are parsed and stored in the leaked structure | before the empty response check triggers the early return. A long- | running TLS client that repeatedly connects to a malicious server | can have its memory exhausted over time. OCSP response checking is | not enabled by default. Only client applications that explicitly | enable the OCSP response check verification flags are affected. | FIPS impact: no The FIPS modules in 4.0 and 3.6 are not affected by | this issue as the affected code is outside the OpenSSL FIPS module | boundary. If you fix the vulnerability please also make sure to include the CVE (Common Vulnerabilities & Exposures) id in your changelog entry. For further information see: [0] https://security-tracker.debian.org/tracker/CVE-2026-54876 https://www.cve.org/CVERecord?id=CVE-2026-54876 [1] https://openssl-library.org/news/secadv/20260805.txt Please adjust the affected versions in the BTS as needed. Regards, Salvatore
