GHSA-ww5h-9m49-7xx4: fast-jwt (CVE-2026-107722)

Package	Ecosystem	Affected	Fixed in
fast-jwt	npm	>=6.2.0, <6.3.0	6.3.0

Machine-written summary

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

The fast-jwt npm package, versions 6.2.0 up to but not including 6.3.0, can still be tricked into RSA-to-HS256 algorithm confusion, because an incomplete fix for CVE-2026-34950 only strips whitespace before PEM detection. An attacker who knows the target's RSA public key can forge tokens that the verifier accepts when the key source has a non-whitespace leading character and no algorithms allowlist is set, which can yield authentication bypass. The source says fast-jwt 6.3.0 fixes the issue, so upgrade to 6.3.0 or later.

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
9.8	Critical	3.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H	CNA (GitHub_M)

CISA KEV Not listed.
EPSS 0.0036, the 29th 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.