Critical severity9.1NVD Advisory· Published Apr 6, 2026· Updated Apr 22, 2026

CVE-2026-34950

Description

fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.1.0 and earlier, the publicKeyPemMatcher regex in fast-jwt/src/crypto.js uses a ^ anchor that is defeated by any leading whitespace in the key string, re-enabling the exact same JWT algorithm confusion attack that CVE-2023-48223 patched.

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LLM-synthesized narrative grounded in this CVE's description and references.

Affected packages

Versions sourced from the GitHub Security Advisory.

Package	Affected versions	Patched versions
fast-jwtnpm	< 6.2.0	6.2.0

Affected products

Nearform/Fast JWT
cpe:2.3:a:nearform:fast-jwt:*:*:*:*:*:node.js:*:*
Range: <6.2.0
ghsa-coords
pkg:npm/fast-jwt
Range: < 6.2.0

Patches

Vulnerability mechanics

References

github.com/nearform/fast-jwt/security/advisories/GHSA-mvf2-f6gm-w987nvdExploitVendor AdvisoryWEB
github.com/advisories/GHSA-c2ff-88x2-x9pgghsaADVISORY
github.com/advisories/GHSA-mvf2-f6gm-w987ghsaADVISORY
nvd.nist.gov/vuln/detail/CVE-2026-34950ghsaADVISORY

News mentions

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cvss	0.591
epss	0.000
exploit	0.000
kev	0.000
patch	-0.070
ransomware	0.000