CVE-2026-5501 — Improper Certificate Signature Verification in X.509 Chain Validation Allows Forged Leaf Certificates

Description (CNA)

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.

Affected (CNA)

Vendor / product	Versions
wolfSSL / wolfSSL	affected 0 through 5.9.0

CWE

CWE-295

References

https://github.com/wolfSSL/wolfssl/pull/10102

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.