CVE-2026-33557
Last modified
CVE-2026-33557 is a critical-severity vulnerability rated 9.1/10 on the CVSS scale. A possible security vulnerability has been identified in Apache Kafka. By default, the broker property `sasl.oauthbearer.jwt.validator.class` is set to `org.apache.kafka.common.security.oauthbearer.DefaultJwtValidator`. It accepts any JWT token without validating its signature, issuer, or audience. EPSS estimates a 0.50% chance of exploitation in the next 30 days.
Description
A possible security vulnerability has been identified in Apache Kafka. By default, the broker property `sasl.oauthbearer.jwt.validator.class` is set to `org.apache.kafka.common.security.oauthbearer.DefaultJwtValidator`. It accepts any JWT token without validating its signature, issuer, or audience. An attacker can generate a JWT token from any issuer with the `preferred_username` set to any user, and the broker will accept it. We advise the Kafka users using kafka v4.1.0 or v4.1.1 to set the config `sasl.oauthbearer.jwt.validator.class` to `org.apache.kafka.common.security.oauthbearer.BrokerJwtValidator` explicitly to avoid this vulnerability. Since Kafka v4.1.2 and v4.2.0 and later, the issue is fixed and will correctly validate the JWT token.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Apache | Kafka | >= 4.1.0, < 4.1.2 |
References
- https://kafka.apache.org/cve-listVendor Advisory
- https://lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953hMitigation, Vendor Advisory
Timeline
- Published
- Last Modified
- Status
- Analyzed
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