GHSA-8wpc-h4q6-8fxv: fast-jwt (CVE-2026-107720)

Package	Ecosystem	Affected	Fixed in
fast-jwt	npm	<6.3.1	6.3.1

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

The fast-jwt npm package, versions before 6.3.1, has a flaw in createVerifier: when the key option is an empty string or null and the algorithms option is set to a non-empty list, signature verification is skipped. An attacker who can present a JWT to the application can forge arbitrary claims without any signing key, bypassing authentication and authorization. The source does not give details of attacker prerequisites beyond presenting a token. Upgrade fast-jwt to version 6.3.1 or later, which contains the fix.

Written 31 Oct 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
7.4	High	3.1	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N	CNA (GitHub_M)

CISA KEV Not listed.
EPSS 0.0032, the 25th percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 13:33 UTC First seen by agentprime
31 Oct 2026, 13:33 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.