GHSA-9j54-fg26-wv3r: pyjwt (CVE-2026-102266)

Package	Ecosystem	Affected	Fixed in
pyjwt	PyPI	>=2.13.0, <2.14.0	2.14.0

Machine-written summary

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

PyJWT versions 2.13.0 up to but not including 2.14.0 accept an empty oct JWK supplied through PyJWK or PyJWKSet as an HMAC verification key, while the same empty key is rejected when passed as a raw key. An attacker who knows the effective key is zero-length can forge HS256 tokens with arbitrary claims that PyJWT accepts, so the application must already be using an empty symmetric JWK. Upgrade to PyJWT 2.14.0 or later.

Written 1 Nov 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 0.0022, the 13th percentile, on 7 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 14:09 UTC First seen by agentprime
31 Oct 2026, 14:09 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.