CVE-2026-33557
CRITICALDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Exploit Intelligence
Moderate risk: more likely to be exploited than 49% of all known CVEs.
References
Related Vulnerabilities
Other CWE-1285 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2025-7848 | High | 7.8 | 4.2% | - | - |
| CVE-2023-46724 | High | 8.6 | 4.0% | - | Fix |
| CVE-2022-21821 | High | 7.8 | 2.0% | - | Fix |
| CVE-2026-2006 | High | 8.8 | 1.1% | - | Fix |
| CVE-2020-25241 | High | 7.5 | 1.0% | - | Fix |
| CVE-2025-3357 | Critical | 9.8 | 0.9% | - | - |
Common questions
How do I fix CVE-2026-33557?
Upgrade kafka to 4.1.2 or later.
Is CVE-2026-33557 being actively exploited?
Not that we know of. CVE-2026-33557 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.68% is the estimated probability that it will be exploited in the next 30 days. That is higher than 49% of all scored CVEs.
How severe is CVE-2026-33557?
CVE-2026-33557 has a CVSS v3 base score of 9.1, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-33557 affect?
Published advisories record a fix for kafka (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-15.