Advisory [CVE-2026-110985] Apache Kafka: Kafka broker using SASL/OAUTHBEARER with the default validator (sasl.oauthbearer.jwt.validator.class=DefaultJwtValidator) selects its implementation from configuration
This security Apache Software Foundation advisory covers CVE-2026-110985; related products: Apache Kafka.
Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.
VulniPulse record published Record updated
Get an email when Apache Software Foundation publishes the next one.
VulniPulse checks Apache Software Foundation's security advisories around the clock and emails you new ones with the severity, the fixed version and the vendor's link. First month free, then US$15/month; we email you before the first charge.
Summary
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):
Affected product named by the advisory: Apache Kafka.
- Apache Kafka 4.1.0 through 4.1.2
- Apache Kafka 4.2.0 through 4.2.1
- Apache Kafka 4.3.0
Official advisory · medium-confidence parse· fetched 3 hours ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists. Confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 3 hours ago·verify at source
Mitigation checklist
- 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.
- 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.
Official advisory · medium-confidence parse· fetched 3 hours ago·verify at source
More Apache Software Foundation advisories
- CVE-2026-114349Oct 28, 2026Apache Kafka: When a broker decodes a compressed record batch, the per-record decoder
- CVE-2026-112375Oct 28, 2026Apache Kafka: authenticated Kafka principal with no authorization grants
- CVE-2026-111551Oct 28, 2026Apache Kafka: Several Kafka deserialization paths read a size or count field from input
- CVE-2026-111496Oct 28, 2026Apache Kafka: Kafka Streams derives its stream-time clock from record timestamps
- CVE-2026-111115Oct 28, 2026Apache Kafka's code-generated readers for flexible protocol versions read a tagged-field
- CVE-2026-111108Oct 28, 2026Apache Kafka's code-generated protocol readers pre-size an array's collection
Android app · Google Play
Monitor future Apache Software Foundation CVEs from your phone.
Choose a whole vendor or a precise platform, then receive matching security advisories by phone notification, email, or both. Coverage follows 34 official vendor sources and 160+ reviewed platform categories.
Discussion(0)
No comments yet. Share field notes, upgrade gotchas, or questions — verify against the vendor advisory before acting on community advice.
Sign in to join the discussion.