Improper Certificate Signature Verification in X.509 Chain Validation Allows Forged Leaf Certificates
Summary
Improper Certificate Signature Verification in X.509 Chain Validation Allows Forged Leaf Certificates
Original description
The description as published by the source.
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.
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-5501 wolfssl
- Ubuntu UBUNTU-CVE-2026-5501 wolfssl
References
- advisory github.com
- advisory nvd.nist.gov
- patch github.com