CVE-2026-45388
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn 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).
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThe OCaml-TLS library's TLS client implementation fails to properly validate the KeyUsage and ExtendedKeyUsage X.509 certificate extensions during the handshake process. This allows an attacker to impersonate a legitimate TLS server using certificates that were not issued for server authentication purposes (e.g., certificates meant for code signing or email encryption).
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify OCaml-TLS installationCheck if OCaml-TLS is present: run 'opam list --installed | grep tls' or inspect your project's opam file or lock file for the tls packageAffected if OCaml-TLS library is installed in the environment
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Determine OCaml-TLS versionRun 'opam list --installed ocaml-tls' to see the installed version, or examine the opam lock file for the tls package version entryAffected if Version is present and below 2.1.0
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Confirm TLS client functionality is usedReview application source code to determine if it uses OCaml-TLS as a TLS client - look for imports of Tls_lwt, Tls_core, or similar TLS client modules and establish connections to external serversAffected if The application acts as a TLS client connecting to remote servers using OCaml-TLS
You are affected if your environment uses OCaml-TLS version below 2.1.0 and functions as a TLS client connecting to servers, since certificates without proper serverAuth ExtendedKeyUsage could be accepted.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedUpgrade OCaml-TLS to version 2.1.0 or later which includes proper validation of KeyUsage and ExtendedKeyUsage extensions in server certificates. If upgrading is not possible immediately, ensure only certificates with proper server authentication extensions (serverAuth in ExtendedKeyUsage) are trusted in the certificate chain.
OCaml-TLS version 2.1.0
- 1. Identify the current version of OCaml-TLS in your project by checking your opam package lock file or opam switch list
- 2. Upgrade OCaml-TLS to version 2.1.0 or later using opam install ocaml-tls -version 2.1.0 or by updating your opam file dependencies
- 3. Rebuild your project to ensure the new TLS library version is linked
- 4. Verify the upgrade was successful by checking the installed version with opam list ocaml-tls
- 5. Run your test suite to confirm no regressions in TLS functionality
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,888.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-45388 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-45388 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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