CVE-2026-110985 (GCVE-0-2026-110985)

Vulnerability from cvelistv5 – Published: 2026-10-28 16:37 – Updated: 2026-10-28 16:37
VLAI
Title
Apache Kafka: Broker silently skips JWT signature verification for SASL/OAUTHBEARER when the JWKS endpoint URL is not configured
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): 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).
Severity
No CVSS data available.
CWE
  • CWE-345 - Insufficient Verification of Data Authenticity and its child
  • CWE-347 - Improper verification of cryptographic signature
  • CWE-1287 - Improper validation of specified type of input
  • CWE-636 - Failing Open
Assigner
apache CNA under the mitre root
CNA scorecard B 76/100 over 1090 records in the last 180 days details
References
URL Tags
https://kafka.apache.org/cve-list vendor-advisory
Impacted products
Vendor Product Version CPE status
Apache Software Foundation Apache Kafka Affected: 4.1.0 , ≤ 4.1.2 (semver)
Affected: 4.2.0 , ≤ 4.2.1 (semver)
Affected: 4.3.0 (semver)
guessed Create a notification for this product.
Show details on NVD website

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