How severe is CVE-2026-35039?

CVE-2026-35039 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-2026-35039 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (12th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-35039?

CVE-2026-35039 affects Nearform Fast-jwt. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-35039?

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-2026-35039 have an EU (EUVD) identifier?

Yes. CVE-2026-35039 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-19380.

When was CVE-2026-35039 published?

CVE-2026-35039 was published on 2026-04-06 and last updated on 2026-06-17.

CVE-2026-35039

CVE-2026-35039 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-345.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
EPSS exploit prediction: 0% (12th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-19380
Weakness: CWE-345
Affected product: Nearform Fast-jwt
Published: 2026-04-06
Last modified: 2026-06-17

Description

fast-jwt provides fast JSON Web Token (JWT) implementation. From 0.0.1 to before 6.2.0, setting up a custom cacheKeyBuilder method which does not properly create unique keys for different tokens can lead to cache collisions. This could cause tokens to be mis-identified during the verification process leading to valid tokens returning claims from different valid tokens and users being mis-identified as other users based on the wrong token. Version 6.2.0 contains a patch.

Frequently asked questions

What is CVE-2026-35039?: fast-jwt provides fast JSON Web Token (JWT) implementation. From 0.0.1 to before 6.2.0, setting up a custom cacheKeyBuilder method which does not properly create unique keys for different tokens can lead to cache collisions. This could cause tokens to be mis-identified during the verification process leading to valid tokens returning claims from different valid tokens and users being mis-identified as other users based on the wrong token. Version 6.2.0 contains a patch.
How severe is CVE-2026-35039?: CVE-2026-35039 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-2026-35039 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (12th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-35039?: CVE-2026-35039 affects Nearform Fast-jwt. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-35039?: 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-2026-35039 have an EU (EUVD) identifier?: Yes. CVE-2026-35039 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-19380.
When was CVE-2026-35039 published?: CVE-2026-35039 was published on 2026-04-06 and last updated on 2026-06-17.

References

Affected products (1)

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

More vulnerabilities in Nearform Fast-jwt

CVE-2026-34950 — Critical (CVSS 9.1): fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.1.0 and earlier, the publicKeyPemMatcher regex in…
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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