GHSA-fch4-3c6x-j4gc: authlib (CVE-2026-114618)

Package	Ecosystem	Affected	Fixed in
authlib	PyPI	<1.9.0	1.9.0

Machine-written summary

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

Authlib versions before 1.9.0 are affected: the default RFC 7523 JWT bearer grant does not require the JWT assertion's audience claim to match the authorization server's token endpoint, only that the claim is present. An attacker who holds a validly issued JWT assertion meant for a different audience, and whose signing key is shared with the target server, could present it to obtain an access token. Upgrade to Authlib 1.9.0 or later, where the fix is listed.

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

CISA KEV Not listed.
EPSS 0.0035, the 28th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 14:07 UTC First seen by agentprime
31 Oct 2026, 14:07 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.