---
cve: "CVE-2026-27962"
severity: "CRITICAL"
cvss: 9.1
epss: "55%"
vendor: "authlib"
kev: false
exploited: false
published: "2026-03-16 18:16:07"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-09-17T12:00:51+02:00"
---

# CVE-2026-27962

> 9.1 CRITICAL · 🧪 PoC

## Beschreibung

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.

## CVSS-Vektor

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

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Keine | good |

## Patch verfügbar (OSV)

- 9266eaa2227ad7e21dc731b2a4a01909aabd934b (Commit)
- a5d4b2d4c9e46bfa11c82f85fdc2bcc0b50ae681 (Commit)

## Referenzen

- <https://github.com/authlib/authlib/security/advisories/GHSA-wvwj-cvrp-7pv5>
- <https://github.com/authlib/authlib/commit/a5d4b2d4c9e46bfa11c82f85fdc2bcc0b50ae681>
- <https://github.com/authlib/authlib/releases/tag/v1.6.9>
- <https://access.redhat.com/errata/RHSA-2026:19375>
- <https://access.redhat.com/errata/RHSA-2026:24853>
- <https://access.redhat.com/errata/RHSA-2026:48085>
- <https://access.redhat.com/errata/RHSA-2026:5665>
- <https://access.redhat.com/errata/RHSA-2026:7314>
- <https://access.redhat.com/security/cve/CVE-2026-27962>
- <https://bugzilla.redhat.com/show_bug.cgi?id=2448164>
- <https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27962.json>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-27962) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_