CVE-2026-27962
Description
A flaw was found in Authlib, a Python library used for creating secure authentication and authorization systems. This vulnerability, known as JWK (JSON Web Key) Header Injection, affects how Authlib verifies digital signatures in JWS (JSON Web Signature) tokens. An attacker can exploit this by creating a specially crafted token that includes their own cryptographic key in the header. When the system attempts to verify this token without a predefined key, it mistakenly uses the attacker's key, allowing them to bypass authentication and gain unauthorized access.
Statement
This critical vulnerability in Authlib's JWS implementation allows unauthenticated attackers to forge JWTs by embedding their own cryptographic key in the token header. Impact is high to confidentiality and integrity as attackers can bypass authentication.
The impact for Red Hat Quay is rated as low because it imports authlib solely as a JWK parsing utility and performs all JWT signature verification through PyJWT, so the vulnerable jws.deserialize_compact() code path is never called.
Red Hat OpenShift AI is not affected, since authlib is only present as a transitive dependency in the dev dependency group and is not included in production image builds, so the vulnerable code is not present in the shipped product.
Red Hat Satellite is not affected, as authlib is only present as a dependency of fastmcp. In Satellite, fastmcp only invokes authlib using jwt.decode() which isn't able to reach the vulnerability condition even with key=none.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 9.1 | N/A | 9.1 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Understanding the Weakness (CWE)
Access Control,Integrity,Confidentiality
Technical Impact: Gain Privileges or Assume Identity; Modify Application Data; Execute Unauthorized Code or Commands
An attacker could gain access to sensitive data and possibly execute unauthorized code.
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