Is CVE-2026-35039 in the CISA KEV catalog?

No. CVE-2026-35039 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-35039?

CVE-2026-35039 has a CVSS v3 base score of 9.1 (CRITICAL).

What is the EPSS score for CVE-2026-35039?

CVE-2026-35039 has an EPSS score of 0.21% (12th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-35039?

Upgrade fast-jwt to 6.1.0 or later.

CVE & CISA-KEV Catalog

CVE-2026-35039

CRITICAL

9.1

CVSS v3

NVD

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.

CWE-345 CWE-706 CWE-1289

How to fix

Remediation Available

fast-jwtNVD

Affected:>= 0.1.0, < 6.1.0Fixed in:6.1.0CVE-2026-35039derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Exploit Intelligence

0.21%probability of exploitation in 30 days

12thpercentile

Low risk: more likely to be exploited than 12% of all known CVEs.

References

Patch1

github.com

Vendor Advisory1

github.com

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-22.