Is CVE-2026-35042 in the CISA KEV catalog?

No. CVE-2026-35042 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-35042?

CVE-2026-35042 has a CVSS v3 base score of 7.5 (HIGH).

What is the EPSS score for CVE-2026-35042?

CVE-2026-35042 has an EPSS score of 0.15% (5th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-35042?

Upgrade fast-jwt to 6.2.0 or later.

CVE & CISA-KEV Catalog

CVE-2026-35042

HIGH

7.5

CVSS v3

NVD

Description

fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.1.0 and earlier, fast-jwt does not validate the crit (Critical) Header Parameter defined in RFC 7515 §4.1.11. When a JWS token contains a crit array listing extensions that fast-jwt does not understand, the library accepts the token instead of rejecting it. This violates the MUST requirement in the RFC.

CWE-345 CWE-636

How to fix

Remediation Available

fast-jwtNVD

Affected:< 6.2.0Fixed in:6.2.0CVE-2026-35042derived 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

ConfidentialityNone

IntegrityHigh

AvailabilityNone

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

Exploit Intelligence

0.15%probability of exploitation in 30 days

5thpercentile

Low risk: more likely to be exploited than 5% of all known CVEs.

References

Exploit1

github.com

Technical Description1

rfc-editor.org

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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 2026-04-10.