{"id":"CVE-2026-110985","revision":"8be23916da1e40e78d97bd869c92bb89","records":[{"revision":"8be23916da1e40e78d97bd869c92bb89","observedAt":"2026-10-28T17:46:48.824+00:00","statement":{"source":"cve-program","id":"CVE-2026-110985","aliases":[],"title":"Apache Kafka: Broker silently skips JWT signature verification for SASL/OAUTHBEARER when the JWKS endpoint URL is not configured","description":"A Kafka broker using SASL/OAUTHBEARER with the default validator\u00A0(sasl.oauthbearer.jwt.validator.class=DefaultJwtValidator) selects its implementation from\u00A0configuration. When sasl.oauthbearer.jwks.endpoint.url is set, the validator verifies the\u00A0JWT signature. When that URL is unset (the default) and no verification key resolver is\u00A0supplied, DefaultJwtValidator silently falls back to ClientJwtValidator, which does not\u00A0verify the JWT signature, algorithm, or issuer - and the broker starts with no warning or\u00A0error. This is the residual of CVE-2026-33557, whose fix restored signature verification\u00A0only on the path where the JWKS endpoint URL is set.\n\n\nImpact:\n\nA broker in this state accepts any structurally valid JWT, including \"alg\":\"none\" tokens. An\u00A0unauthenticated remote attacker who can reach the listener can forge a token asserting any\u00A0principal - including configured superusers - and gain full access to the cluster. Only\u00A0brokers that enable SASL/OAUTHBEARER validation without a JWKS endpoint URL (and without a\u00A0custom verification key resolver) are affected; brokers that set the URL verify signatures\u00A0and are not affected. Unlike CVE-2026-110952 (issuer/audience not enforced by default), here\u00A0no signature is verified at all.\n\n\nMitigation (all affected versions, no upgrade required):\n\nSet sasl.oauthbearer.jwks.endpoint.url for every listener/mechanism that uses\u00A0OAuthBearerValidatorCallbackHandler, or configure a signature-verifying\u00A0sasl.oauthbearer.jwt.validator.class.\n\nResolution:\n\nFrom Apache Kafka 4.2.2, 4.3.1, and 4.4.0: a broker that would fall back to the\u00A0non-verifying ClientJwtValidator fails to start with a ConfigException instead of running\u00A0without signature verification (secure by default).","state":0,"publishedAt":"2026-10-28T16:37:45.688+00:00","modifiedAt":"2026-10-28T16:37:45.688+00:00","affected":[{"ecosystem":"https://repo.maven.apache.org/maven2","name":"org.apache.kafka:kafka","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"Apache Software Foundation\",\n                    \"product\": \"Apache Kafka\",\n                    \"packageURL\": \"pkg:maven/org.apache.kafka/kafka\",\n                    \"versions\": [\n                        {\n                            \"status\": \"affected\",\n                            \"version\": \"4.1.0\",\n                            \"lessThanOrEqual\": \"4.1.2\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"status\": \"affected\",\n                            \"version\": \"4.2.0\",\n                            \"lessThanOrEqual\": \"4.2.1\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"status\": \"affected\",\n                            \"version\": \"4.3.0\",\n                            \"versionType\": \"semver\"\n                        }\n                    ],\n                    \"defaultStatus\": \"unaffected\",\n                    \"collectionURL\": \"https://repo.maven.apache.org/maven2\",\n                    \"packageName\": \"org.apache.kafka:kafka\"\n                }"}],"metrics":[],"references":["https://kafka.apache.org/cve-list"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-110985","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-110985","identifiers":["CVE-2026-110985"]},"retained":false,"historicalAffected":[]}],"coverage":[]}