OpenSSL Security Advisory: CVE-2023-54876 Client-Side Memory Leak in OCSP Response Check

OpenSSL Security Advisory [August 15, 2023] Client-side memory leak in OCSP response checking (CVE-2023-54876) Severity: Low Summary: A malicious TLS server can cause a memory leak in a TLS server with OCSP response checking enabled by sending an OCSP response containing no single response entries. Impact: An attacker can leak an adjustable amount of memory in the victim client application. Long-running clients that repeatedly connect to a malicious server may exhaust memory, leading to a denial of service. CWE: CWE-401: Missing Release of Memory after Effective Lifetime Description: The affected function is called when OCSP response checking is enabled. For example, when a TLS client validates a certificate in the server chain using the or verification flags. When the received contains an empty sequence, it is allowed to pass through the network and accepted by the OpenSSL decoder. Memory allocated for the structure is not freed because of the OCSP response returns early, bypassing the cleanup code. An attacker can amplify the amount of memory leaked per handshake by filling the field of the with additional entries. These certificates are parsed and stored in the leaked memory structure until the OCSP response checking triggers the early return. Long-running TLS clients that repeatedly connect to a malicious server may exhaust memory. OCSP response checking is disabled by default. Only client applications that explicitly enable the OCSP response checking verification flags are affected. FIPS impact: None The FIPS module in 4.0 and 3.6 is not affected by this issue because the affected code lies outside the OpenSSL FIPS module boundary. Affected versions: OpenSSL 3.5, 3.4, 3.0, 3.1, 3.2, and 3.3 are vulnerable to this issue because the affected functionality does not exist in these versions. Resolution: OpenSSL 4.0 users should upgrade to the OpenSSL 4.0.2 release. OpenSSL 3.6 users should upgrade to the OpenSSL 3.6.4 release. Due to the low severity of this issue, we will not release a new version of OpenSSL. The fix will be included in the next release of the 4.0 and 3.6 branches, once available. The fix is also included in commit d8c3104 (for 4.0) and commit 15595fe (for 3.6) in the OpenSSL git repository. This issue was reported by Bhabani Sankar Das on June 15, 2024, and independently by Zhenghe Shen on June 19, 2024. The fix was developed by Mounir Idrissi.

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OpenSSL Security Advisory: CVE-2023-54876 Client-Side Memory Leak in OCSP Response Check