CVE-2026-33557
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.
Scoring
- Severity
- HIGH
- CVSS base score
- 8.6
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
- EPSS probability
- 0.68%
- CWE
- CWE-1285
- Published
- 2026-04-20
- Last modified
- 2026-07-15
Affected products
- Apache Software Foundation Apache Kafka
Weakness type
Related vulnerabilities
- CVE-2026-31912 — OOBR in libpcap before 1.10.7
- CVE-2026-53530 — ratex-parser panics on `\verb` with a multibyte delimiter (UTF-8 byte-boundary slice)
- CVE-2026-14479 — Denial of Service in Autodesk Installer IPC Channel
- CVE-2026-18485 — Local Privilege Escalation in NI-PAL
- CVE-2026-12681 — Improper Validation of Specified Index, Position, or Offset in Input vulnerability in Google...
- CVE-2026-8036 — Local privilege escalation in NI-PAL
- CVE-2026-45352 — cpp-httplib DoS: Negative chunk-size in chunked Transfer-Encoding
- CVE-2026-9100 — Heap memory out of bounds read and crash in C Driver legacy GridFS file reader