GHSA-3fvg-4v2m-98jf is a high-severity (CVSS 8.6) CWE-347 vulnerability in jsrsasign. 4 public exploit references exist, so weaponization risk is real. A fix is available for jsrsasign — see the affected versions and patch details below.
JWS and JWT signature validation vulnerability with special characters
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
GHSA-3fvg-4v2m-98jf 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 378,567 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, a proxy for how much of the ecosystem is exposed.
jsrsasignnpmDescription
Impact
Jsrsasign supports JWS(JSON Web Signatures) and JWT(JSON Web Token) validation. However JWS or JWT signature with non Base64URL encoding special characters or number escaped characters may be validated as valid by mistake.
For example, even if a string of non Base64URL encoding characters such as !@$% or \11 is inserted into a valid JWS or JWT signature value string, it will still be a valid JWS or JWT signature by mistake.
When jsrsasign's JWS or JWT validation is used in OpenID connect or OAuth2, this vulnerability will affect to authentication or authorization.
By our internal assessment, CVSS 3.1 score will be 8.6. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N
Patches
Users validate JWS or JWT signatures should upgrade to 10.5.25.
Workarounds
Validate JWS or JWT signature if it has Base64URL and dot safe string before executing JWS.verify() or JWS.verifyJWT() method.
ACKNOWLEDGEMENT
Thanks to Adi Malyanker and Or David for this vulnerability report. Also thanks for Snyk security team for this coordination.
References
https://github.com/kjur/jsrsasign/releases/tag/10.5.25 https://github.com/kjur/jsrsasign/security/advisories/GHSA-3fvg-4v2m-98jf kjur's advisories https://github.com/advisories/GHSA-3fvg-4v2m-98jf github advisories https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-25898 https://kjur.github.io/jsrsasign/api/symbols/KJUR.jws.JWS.html#.verifyJWT https://kjur.github.io/jsrsasign/api/symbols/KJUR.jws.JWS.html#.verify https://kjur.github.io/jsrsasign/api/symbols/global__.html#.isBase64URLDot https://github.com/kjur/jsrsasign/wiki/Tutorial-for-JWS-verification https://github.com/kjur/jsrsasign/wiki/Tutorial-for-JWT-verification https://security.snyk.io/vuln/SNYK-JS-JSRSASIGN-2869122
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | jsrsasign | ≥ 4.8.0&&< 10.5.25 | 10.5.25npm install jsrsasign@10.5.25 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
The package jsrsasign before 10.5.25 are vulnerable to Improper Verifica…
The package jsrsasign before 10.5.25 are vulnerable to Improper Verifica…
The package jsrsasign before 10.5.25 are vulnerable to Improper Verifica…
The package jsrsasign before 10.5.25 are vulnerable to Improper Verifica…
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for jsrsasign, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update jsrsasign to 10.5.25 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-3fvg-4v2m-98jf 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 GHSA-3fvg-4v2m-98jf can be triaged on real exposure rather than presence alone.
Tailored to GHSA-3fvg-4v2m-98jf. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-3fvg-4v2m-98jf in your dependencies?
O3 Security finds GHSA-3fvg-4v2m-98jf across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.