CVE-2026-110985
UNSCOREDDescription
A Kafka broker using SASL/OAUTHBEARER with the default validator (sasl.oauthbearer.jwt.validator.class=DefaultJwtValidator) selects its implementation from configuration. When sasl.oauthbearer.jwks.endpoint.url is set, the validator verifies the JWT signature. When that URL is unset (the default) and no verification key resolver is supplied, DefaultJwtValidator silently falls back to ClientJwtValidator, which does not verify the JWT signature, algorithm, or issuer - and the broker starts with no warning or error. This is the residual of CVE-2026-33557, whose fix restored signature verification only on the path where the JWKS endpoint URL is set. Impact: A broker in this state accepts any structurally valid JWT, including "alg":"none" tokens. An unauthenticated remote attacker who can reach the listener can forge a token asserting any principal - including configured superusers - and gain full access to the cluster. Only brokers that enable SASL/OAUTHBEARER validation without a JWKS endpoint URL (and without a custom verification key resolver) are affected; brokers that set the URL verify signatures and are not affected. Unlike CVE-2026-110952 (issuer/audience not enforced by default), here no signature is verified at all. Mitigation (all affected versions, no upgrade required): Set sasl.oauthbearer.jwks.endpoint.url for every listener/mechanism that uses OAuthBearerValidatorCallbackHandler, or configure a signature-verifying sasl.oauthbearer.jwt.validator.class. Resolution: From Apache Kafka 4.2.2, 4.3.1, and 4.4.0: a broker that would fall back to the non-verifying ClientJwtValidator fails to start with a ConfigException instead of running without signature verification (secure by default).
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3.1 Vector
No CVSS vector data available.
Exploit Intelligence
Low risk: more likely to be exploited than 2% of all known CVEs.
References
Related Vulnerabilities
Other CWE-345 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2023-38831 | High | 7.8 | 100% | KEV + Ransom | Fix |
| CVE-2016-4553 | High | 8.6 | 80% | - | Fix |
| CVE-2016-4554 | High | 8.6 | 39% | - | Fix |
| CVE-2023-35719 | Medium | 6.8 | 25% | - | - |
| CVE-2022-26871 | Critical | 9.8 | 19% | KEV | - |
| CVE-2025-51471 | Medium | 6.9 | 19% | - | - |
Common questions
How do I fix CVE-2026-110985?
No published fix for CVE-2026-110985 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-110985 being actively exploited?
Not that we know of. CVE-2026-110985 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.13% is the estimated probability that it will be exploited in the next 30 days. That is higher than 2% of all scored CVEs.
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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 2026-10-29.