CVE-2026-45388 json
TLS-client (with TLS 1.3) does insufficient certificate checks (missing KeyUsage and ExtendedKeyUsage validation)
published 2026-05-20 5 mo ago modified 2026-11-06 2 d ago also EUVD-2026-36764 , OSEC-2026-06
- cvss
- 9.1
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 13%
- public exploits
- 0
- none known
Summary
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).
Patch / fix
- opam tls 2.1.0
CISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- yes
- Technical impact
- total
- Assessed
- 4 mo ago
Exploit prediction
0.22% chance of exploitation in the next 30 days, higher than 13% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- osv.dev https://osv.dev/vulnerability/OSEC-2026-06 referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CISA ADP | 3.1 | 9.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |
| CNA | 3.1 | 9.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |
| OSV | 3.1 | 7.4 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| opam | tls | <2.1.0 |
2.1.0 |
Classification
- Weakness
-
- CWE-295 Improper Certificate Validation
References
Sources
- CVE List CVE-2026-45388
- NVD CVE-2026-45388
- OSV OSEC-2026-06
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