CVE-2022-23540 is a medium-severity (CVSS 6.4) Improper Authentication vulnerability in jsonwebtoken. A fix is available for jsonwebtoken — see the affected versions and patch details below.
jsonwebtoken vulnerable to signature validation bypass due to insecure default algorithm in jwt.verify()
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2022-23540.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2022-23540 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,238 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
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 | 9.0.0npm install jsonwebtoken@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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2022-23540 can be triaged on real exposure rather than presence alone.
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.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| RHODF-4.13-RHEL-9 | odf4/mcg-core-rhel9:v4.13.0-41 | RHSA-2023:3742 |
Frequently Asked Questions
Is CVE-2022-23540 in your dependencies?
O3 Security finds CVE-2022-23540 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.