CVE-2022-23540
MEDIUMCVE-2022-23540 is a medium-severity (CVSS 6.4) Improper Authentication vulnerability in jsonwebtoken. O3 Security confirms whether CVE-2022-23540 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
jsonwebtoken vulnerable to signature validation bypass due to insecure default algorithm in jwt.verify()
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
jsonwebtokennpmDescription
In versions <=8.5.1 of jsonwebtoken library, lack of algorithm definition in the jwt.verify() function can lead to signature validation bypass due to defaulting to the none algorithm for signature verification. Users are affected if you do not specify algorithms in the jwt.verify() function. This issue has been fixed, please update to version 9.0.0 which removes the default support for the none algorithm in the jwt.verify() method. There will be no impact, if you update to version 9.0.0 and you don’t need to allow for the none algorithm. If you need 'none' algorithm, you have to explicitly specify that in jwt.verify() options.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | jsonwebtoken | all versions | 9.0.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for jsonwebtoken. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update jsonwebtoken to 9.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-23540 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2022-23540 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2022-23540. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2022-23540 in your dependencies?
O3 detects CVE-2022-23540 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.