EUVD-2026-36765

In OCaml-TLS before 2.1.0, the server implementation does insufficient checks of the certificate provided by the client when doing client authentication, which allows impersonation with certificates that are not meant for client authentication because of KeyUsage and ExtendedKeyUsage...

CVE-2026-45388

In OCaml-TLS before 2.1.0, the client implementation does insufficient checks of the certificate provided by the server, which allows impersonation with certificates that are not meant for server authentication because of KeyUsage and ExtendedKeyUsage...

CVE-2026-45389

In OCaml-TLS before 2.1.0, the server implementation does insufficient checks of the certificate provided by the client when doing client authentication, which allows impersonation with certificates that are not meant for client authentication because of KeyUsage and ExtendedKeyUsage...

CVE-2026-45389

In OCaml-TLS before 2.1.0, the server implementation does insufficient checks of the certificate provided by the client when doing client authentication, which allows impersonation with certificates that are not meant for client authentication because of KeyUsage and ExtendedKeyUsage...

CVE-2026-45388

CVE-2026-45388 affects OCaml-TLS before 2.1.0. The TLS 1.3 client path in handshake_client13.ml did not wire into validate_keyusage, allowing a certificate issued for non-server purposes (e.g., clientAuth, codeSigning, emailProtection) to impersonate a TLS server if the EKU/KeyUsage restrictions ...

CVE-2026-45389

In OCaml-TLS before 2.1.0, the server implementation does insufficient checks of the certificate provided by the client when doing client authentication, which allows impersonation with certificates that are not meant for client authentication because of KeyUsage and ExtendedKeyUsage...

CVE-2026-45389

Summary (OCaml-TLS CVE-2026-45389): OCaml-TLS versions before 2.1.0 fail to properly validate KeyUsage and ExtendedKeyUsage on client certificates during mutual TLS, allowing impersonation with certificates intended for server authentication. The issue arises in the server-side certificate valida...

OSEC-2026-06 TLS-client (with TLS 1.3) does insufficient certificate checks (missing KeyUsage and ExtendedKeyUsage validation)

The ocaml-TLS 1.3 client does not validate the KeyUsage and ExtendedKeyUsage extensions of the server certificate. This can lead to impersonation with a certificate issued to a client. Scenario Every employee at a major bank carries a smart card. The card holds a clientAuth certificate issued by...

PT-2026-42202

Name of the Vulnerable Software and Affected Versions OCaml-TLS versions prior to 2.1.0 Description The client implementation in OCaml-TLS fails to properly validate the KeyUsage and ExtendedKeyUsage EKU extensions of server certificates during TLS 1.3 handshakes. Specifically, the answer...