OCaml-TLS Client Certificate Validation Bypass

Publication date: 2026-06-15

Last updated on: 2026-06-16

Assigner: MITRE

Description

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).

CVSS Scores

EPSS Scores

Probability:
Percentile:

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-2026-45388

EUVD

EUVD-2026-36764

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-295	The product does not validate, or incorrectly validates, a certificate.

Attack-Flow Graph

Executive Summary

This vulnerability exists in OCaml-TLS versions before 2.1.0. The client implementation does not properly verify the server's certificate, specifically failing to check the KeyUsage and ExtendedKeyUsage fields. This flaw allows an attacker to impersonate a server using certificates that are not intended for server authentication.

Impact Analysis

Because the client does not correctly validate server certificates, an attacker could impersonate a legitimate server. This could lead to man-in-the-middle attacks, where sensitive information might be intercepted or altered without the user's knowledge.

Hi! I’m here to help you understand CVE-2026-45388. Ask me anything about the vulnerability, its impact, or mitigation strategies.

0/70