CVE-2026-33557
Description
A flaw was found in Apache Kafka. By default, the sasl.oauthbearer.jwt.validator.class property is set to org.apache.kafka.common.security.oauthbearer.DefaultJwtValidator, which does not validate JSON Web Token (JWT) signatures, issuers, or audiences. A remote attacker can exploit this by crafting a malicious JWT token with an arbitrary preferred_username, leading to an authentication bypass and unauthorized access to the Kafka broker.
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).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.6 | N/A | 8.6 |
| 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 | Low | N/A | Low |
| Availability Impact | Low | N/A | Low |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
Understanding the Weakness (CWE)
Access Control
Technical Impact: Bypass Protection Mechanism
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