How severe is CVE-2026-34950?

CVE-2026-34950 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2026-34950 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (14th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-34950?

CVE-2026-34950 affects Nearform Fast-jwt. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-34950?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-34950 have an EU (EUVD) identifier?

Yes. CVE-2026-34950 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-19356.

When was CVE-2026-34950 published?

CVE-2026-34950 was published on 2026-04-06 and last updated on 2026-06-17.

CVE-2026-34950

CVE-2026-34950 is a critical-severity vulnerability in Nearform Fast-jwt with a CVSS 3.x base score of 9.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-327.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
EPSS exploit prediction: 0% (14th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-19356
Weakness: CWE-327
Affected product: Nearform Fast-jwt
Published: 2026-04-06
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-34950?: 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.
How severe is CVE-2026-34950?: CVE-2026-34950 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2026-34950 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (14th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-34950?: CVE-2026-34950 affects Nearform Fast-jwt. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-34950?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-34950 have an EU (EUVD) identifier?: Yes. CVE-2026-34950 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-19356.
When was CVE-2026-34950 published?: CVE-2026-34950 was published on 2026-04-06 and last updated on 2026-06-17.

References

https://github.com/nearform/fast-jwt/security/advisories/GHSA-mvf2-f6gm-w987

Affected products (1)

cpe:2.3:a:nearform:fast-jwt:*:*:*:*:*:node.js:*:*

More vulnerabilities in Nearform Fast-jwt

CVE-2026-35039 — Critical (CVSS 9.1): fast-jwt provides fast JSON Web Token (JWT) implementation. From 0.0.1 to before 6.2.0, setting up a custom…
CVE-2026-35042 — High (CVSS 7.5): fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.1.0 and earlier, fast-jwt does not validate the crit…
CVE-2023-48223 — Medium (CVSS 5.9): fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to version 3.3.2, the fast-jwt library does not…
CVE-2026-35040 — Medium (CVSS 5.3): fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.2.1, using certain modifiers on RegExp objects…
CVE-2026-35041 — Medium (CVSS 4.2): fast-jwt provides fast JSON Web Token (JWT) implementation. From 5.0.0 to 6.2.0, a denial-of-service condition exists…

All CVEs affecting Nearform Fast-jwt →

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