wolfSSL up to 5.9.0 OpenSSL Compatibility API wolfSSL_X509_verify_cert certificate validation

Summaryinfo

A vulnerability described as critical has been identified in wolfSSL up to 5.9.0. This issue affects the function wolfSSL_X509_verify_cert of the component OpenSSL Compatibility API. Such manipulation leads to certificate validation. This vulnerability is referenced as CVE-2026-5501. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in wolfSSL up to 5.9.0. Affected by this issue is the function wolfSSL_X509_verify_cert of the component OpenSSL Compatibility API. The manipulation with an unknown input leads to a certificate validation vulnerability. Using CWE to declare the problem leads to CWE-295. The product does not validate, or incorrectly validates, a certificate. Impacted is integrity. CVE summarizes:

wolfSSL_X509_verify_cert in the OpenSSL compatibility layer accepts a certificate chain in which the leaf's signature is not checked, if the attacker supplies an untrusted intermediate with Basic Constraints `CA:FALSE` that is legitimately signed by a trusted root. An attacker who obtains any leaf certificate from a trusted CA (e.g. a free DV cert from Let's Encrypt) can forge a certificate for any subject name with any public key and arbitrary signature bytes, and the function returns `WOLFSSL_SUCCESS` / `X509_V_OK`. The native wolfSSL TLS handshake path (`ProcessPeerCerts`) is not susceptible and the issue is limited to applications using the OpenSSL compatibility API directly, which would include integrations of wolfSSL into nginx and haproxy.

The weakness was published by Calif.io. The advisory is available at github.com. This vulnerability is handled as CVE-2026-5501 since 04/03/2026. The exploitation is known to be difficult. The attack may be launched remotely. No form of authentication is required for exploitation. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 04/10/2026). This vulnerability is assigned to T1587.003 by the MITRE ATT&CK project.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Name

• wolfSSL

Version

• 5.0
• 5.1
• 5.2
• 5.3
• 5.4
• 5.5
• 5.6
• 5.7
• 5.8
• 5.9.0

License

• open-source

Website

• Product: https://github.com/wolfSSL/wolfssl/

CPE 2.3info

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Entryinfo

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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