OCaml-TLS Client Authentication Certificate Impersonation

Publication date: 2026-06-15

Last updated on: 2026-06-16

Assigner: MITRE

Description

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).

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-06-15

Last Modified

2026-06-16

Generated

2026-07-06

AI Q&A

2026-06-15

EPSS Evaluated

2026-07-04

NVD

CVE-2026-45389

EUVD

EUVD-2026-36765

Affected Vendors & Products

Vendor	Product	Version / Range
ocaml_tls	ocaml_tls	to 2.1.0 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability exists in OCaml-TLS versions before 2.1.0. The server implementation does not properly verify the certificate provided by the client during client authentication. Specifically, it fails to check whether the certificate is intended for client authentication based on its KeyUsage and ExtendedKeyUsage fields.

Impact Analysis

Because the server does insufficient checks on client certificates, an attacker could impersonate a client using a certificate that is not meant for client authentication. This could lead to unauthorized access or impersonation in systems relying on OCaml-TLS for secure client authentication.

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