CVE-2026-33557
A possible security vulnerability has been identified in Apache Kafka.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.68%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 9.1 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- EPSS
- 0.68% probability · 51th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-1285, CWE-303
- Affected
- apache/kafka
- Source
- security@apache.org
References
- https://kafka.apache.org/cve-listVendor Advisory
- https://lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953hMitigation, Vendor Advisory
- http://www.openwall.com/lists/oss-security/2026/04/17/2Mailing List
- https://access.redhat.com/security/cve/CVE-2026-33557
- https://bugzilla.redhat.com/show_bug.cgi?id=2459739
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33557.json
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.