CVE-2026-33557
What it is
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.
At a glance
- Exploitability
- Can be exploited over the network without logging in. High risk of data exposure, data tampering.
- Exploit odds
- 0.9% chance of exploitation in the next 30 days (EPSS).
- Fix
- A patch, advisory or fixed version is referenced. Upgrade or apply it.
Timeline
- PublishedDisclosed publicly on CVE.org and NVD
- Last updatedMost recent change to the record
Why it ranks here
- Exploited in the wild: no, CISA does not list it.
- Exploit odds: 0.9% in the next 30 days (EPSS).
- Severity: 9.1 CRITICAL (CVSS).
- Fix: a patch or advisory is linked.
Details
- Published
- Last modified
- Exploit probability
- 0.9% · EPSS, next 30 days
- Weakness
- CWE-1285
- Record status
- Modified
Affected
- Apache Kafka < 4.1.2
Attack profile CVSS 3.1 · 9.1
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Is it in your code?
Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.
Read https://cve-list.com/agent/cve/CVE-2026-33557.md and follow it. Check whether this project is affected by CVE-2026-33557. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.
Fix and advisories
References
- https://kafka.apache.org/cve-list
- https://lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953h
- http://www.openwall.com/lists/oss-security/2026/04/17/2
- 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