CVE-2026-5447: 
wolfSSL vulnerability analysis and mitigation

CVE-2026-5447 is a heap-based buffer overflow vulnerability in the wolfSSL cryptographic library affecting the CertFromX509 function. The flaw arises from incorrect size handling of the AuthorityKeyIdentifier (AKID) extension when converting an X.509 certificate internally, leading to a heap buffer overflow condition. All wolfSSL versions prior to 5.9.1 are affected. The CVE was published on April 9, 2026, with the fix merged on April 3, 2026. It carries a CVSS v3.1 base score of 7.5 (High) and a CVSS v4.0 base score of 6.3 (Medium) (GitHub Advisory, wolfSSL PR).

The root cause is classified as CWE-122 (Heap-based Buffer Overflow) and CWE-131 (Incorrect Calculation of Buffer Size). Specifically, when the WOLFSSL_AKID_NAME feature is enabled, the CertFromX509 function in src/x509.c fails to validate the actual copied length of the raw AuthorityKeyIdentifier extension before copying it into cert->akid, allowing a heap overflow if the extension size exceeds the allocated buffer. An attacker can trigger this by supplying a crafted X.509 certificate with an intentionally oversized AKID extension — exploitable over the network without authentication or user interaction, though attack requirements (AT:P) indicate some deployment-specific preconditions must be met. The fix adds explicit bounds checks for authKeyIdSrcSz and authKeyIdSz before the copy operation, and a regression test (test_x509_CertFromX509_akid_overflow) was added to validate the safe rejection of oversized AKID extensions (wolfSSL PR, GitHub Advisory).

Successful exploitation can result in heap memory corruption on systems that process X.509 certificates using wolfSSL with the WOLFSSL_AKID_NAME feature enabled. The primary assessed impact is to integrity (rated High under CVSS v3.1), with no direct confidentiality or availability impact identified in the current scoring. In practice, heap overflows of this nature can potentially be leveraged for arbitrary code execution or denial of service depending on heap layout and exploitation sophistication, though no such escalation has been demonstrated publicly (GitHub Advisory, wolfSSL PR).

There is no public proof-of-concept exploit and no evidence of in-the-wild exploitation at this time. The EPSS score is approximately 0.033–0.035%, placing it in the 11th percentile for exploitation likelihood within 30 days. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. No threat actor attribution has been reported (GitHub Advisory, Feedly).

The vulnerability is patched in wolfSSL version 5.9.1 and later (targeted for release 5.9.2 per the PR label). Users should upgrade to wolfSSL 5.9.1 or above as the primary remediation. As a temporary workaround, organizations can disable the WOLFSSL_AKID_NAME compile-time feature if not required, or restrict processing of X.509 certificates from untrusted sources. A backport patch for embedded/OpenEmbedded environments was also published by the meta-openembedded project (wolfSSL PR, Red Hat Bugzilla).

Red Hat tracked the vulnerability via their security response process (Bugzilla bug 2457074) with a medium severity rating. The oss-security mailing list carried a disclosure post in Q2 2026. VulnCheck published a blog post referencing this CVE in the context of Anthropic-credited CVE discoveries, noting it as part of a broader AI-assisted vulnerability research effort (Red Hat Bugzilla, oss-sec, VulnCheck Blog).