CVE-2026-35042: fast-jwt provides fast JSON Web Token (JWT) implementation

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

fast-jwt: upgrade to 6.2.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-35042 being exploited?

CVE-2026-35042 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-35042 affect?

CVE-2026-35042 affects fast-jwt. Severity is 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 (Critical) Header Parameter defined in RFC 7515 §4.1.11. When a JWS token contains a crit array listing extensions that fa

Q: How urgent is CVE-2026-35042?

Priority 39/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADE

CVE-2026-35042 is a high-severity flaw (CVSS 7.5) affecting fast-jwt. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 91%)
CISA exploited list	No
Weakness	CWE-345, CWE-636
Published	2026-04-06
Last modified	2026-10-24

Publisher (CNA): GitHub, Inc. · Vendor: nearform

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-06 17:17 UTCPublished CVE record published
2026-10-24 13:10 UTCUpdated Record last modified

nearform fast-jwt UPGRADE

Affected: < 6.2.0

Fixed in: 6.2.0

Safe to downgrade to: no unaffected older release

1. Check installed version

npm ls fast-jwt

2. UPGRADE to 6.2.0

npm install fast-jwt@">=6.2.0"

Exact fixes by distribution

npm · fast-jwt · NO FIX YET · vulnerable: <= 6.1.0 · source

Fedora ELN · ntpd-rs · FIXED · 1.7.2-3.eln159 · FEDORA-2026-57e4a99310 · source

sudo dnf upgrade --advisory=FEDORA-2026-57e4a99310

Fedora 46 · moby-engine · FIXED · 29.9.2-2.fc46 · FEDORA-2026-4856be87b3 · source

sudo dnf upgrade --advisory=FEDORA-2026-4856be87b3

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: github.com/nearform/fast-jwt/security/advisories/GHSA-hm7r-c7qw-ghp6

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-35042?

fast-jwt: upgrade to 6.2.0. Exact commands for each OS are on this page.

Is CVE-2026-35042 being exploited?

CVE-2026-35042 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-35042 affect?

CVE-2026-35042 affects fast-jwt. Severity is 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 (Critical) Header Parameter defined in RFC 7515 §4.1.11. When a JWS token contains a crit array listing extensions that fa

How urgent is CVE-2026-35042?

Priority 39/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-35039 CRITICAL 9.1 UPGRADE fast-jwt provides fast JSON Web Token (JWT) implementation

References

← Back to latest CVEs