CVE-2026-27962

unknown

Published 2026-03-16 · Modified 2026-04-21

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CVSS v3

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CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

CVSS v4 NEW

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not yet in upstream

VIR risk

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Description

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a JWK Header Injection vulnerability in authlib's JWS implementation allows an unauthenticated attacker to forge arbitrary JWT tokens that pass signature verification. When key=None is passed to any JWS deserialization function, the library extracts and uses the cryptographic key embedded in the attacker-controlled JWT jwk header field. An attacker can sign a token with their own private key, embed the matching public key in the header, and have the server accept the forged token as cryptographically valid — bypassing authentication and authorization entirely. This issue has been patched in version 1.6.9.

Predictions

Exploit likelihood

30%

Patch ETA

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Heuristic predictions, AS-IS, for prioritization only.

Mitigations

No mitigations published for this CVE yet.

The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.

✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here with source_tier=community-verified.

OS impact

SUSE Affected 1 release

Version	Status	Fixed in
—	Affected	—

Debian Mixed 5 releases

Version	Status	Fixed in
trixie	Affected	—
sid	Fixed	`1.6.9-1`
forky	Fixed	`1.6.9-1`
bullseye	Fixed	`0.15.4-1+deb11u2`
bookworm	Affected	—

Package impact

Ecosystem	Package	Vulnerable	Fixed
PyPI	authlib	`<1.6.9`	`1.6.9`

References

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.