CVE-2026-27962

Publication date 16 March 2026

Last updated 16 July 2026

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

9.1 · Critical

Score breakdown

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.

Status

Package Ubuntu Release Status
python-authlib 26.04 LTS resolute
Fixed 1.6.7-1ubuntu0.1~esm1
25.10 questing Ignored end of life, was needs-triage
24.04 LTS noble
Fixed 1.3.0-1ubuntu0.1~esm2
22.04 LTS jammy
Fixed 0.15.5-1ubuntu0.1~esm2

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Patch details

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Package Patch details
python-authlib

Severity score breakdown

CVSS version: CVSS v3.0

Base score 9.1 · Critical

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

References

Related Ubuntu Security Notices (USN)

Other references

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