CVE-2026-35042

Q: How do I fix CVE-2026-35042?

Upgrade fast-jwt to 6.2.0 or later.

Q: Is CVE-2026-35042 being actively exploited?

Not that we know of. CVE-2026-35042 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.15% is the estimated probability that it will be exploited in the next 30 days. That is higher than 5% of all scored CVEs.

Q: How severe is CVE-2026-35042?

CVE-2026-35042 has a CVSS v3 base score of 7.5, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

Q: What does CVE-2026-35042 affect?

Published advisories record a fix for fast-jwt (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

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

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

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

Related Vulnerabilities

Other CWE-345 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-38831	High	7.8	98%	KEV + Ransom	Fix
CVE-2016-4553	High	8.6	79%	-	Fix
CVE-2016-4554	High	8.6	40%	-	Fix
CVE-2023-35719	Medium	6.8	26%	-	-
CVE-2022-26871	Critical	9.8	20%	KEV	-
CVE-2014-4936	High	9.3	17%	-	-

Common questions

How do I fix CVE-2026-35042?

Upgrade fast-jwt to 6.2.0 or later.

Is CVE-2026-35042 being actively exploited?

Not that we know of. CVE-2026-35042 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.15% is the estimated probability that it will be exploited in the next 30 days. That is higher than 5% of all scored CVEs.

How severe is CVE-2026-35042?

CVE-2026-35042 has a CVSS v3 base score of 7.5, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2026-35042 affect?

Published advisories record a fix for fast-jwt (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

Embed a live status badge for CVE-2026-35042

Markdown

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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.