{"api_version":"1","generated_at":"2026-10-28T18:48:34+00:00","cve":"CVE-2026-110985","urls":{"html":"https://cve.report/CVE-2026-110985","api":"https://cve.report/api/cve/CVE-2026-110985.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-110985","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-110985"},"summary":{"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 (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.\n\n\nImpact:\n\nA 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.\n\n\nMitigation (all affected versions, no upgrade required):\n\nSet sasl.oauthbearer.jwks.endpoint.url for every listener/mechanism that uses OAuthBearerValidatorCallbackHandler, or configure a signature-verifying sasl.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 non-verifying ClientJwtValidator fails to start with a ConfigException instead of running without signature verification (secure by default).","state":"PUBLISHED","assigner":"apache","published_at":"2026-10-28 17:17:38","updated_at":"2026-10-28 17:17:38"},"problem_types":["CWE-345","CWE-347","CWE-636","CWE-1287","CWE-345 CWE-345 Insufficient Verification of Data Authenticity and its child","CWE-347 CWE-347 Improper verification of cryptographic signature","CWE-1287 CWE-1287 Improper validation of specified type of input","CWE-636 CWE-636 Failing Open"],"metrics":[],"references":[{"url":"https://kafka.apache.org/cve-list","name":"https://kafka.apache.org/cve-list","refsource":"security@apache.org","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-110985","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-110985","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Apache Software Foundation","product":"Apache Kafka","version":"affected 4.1.0 4.1.2 semver","platforms":[]},{"source":"CNA","vendor":"Apache Software Foundation","product":"Apache Kafka","version":"affected 4.2.0 4.2.1 semver","platforms":[]},{"source":"CNA","vendor":"Apache Software Foundation","product":"Apache Kafka","version":"affected 4.3.0 semver","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[{"source":"CNA","value":"San Zhang ","lang":"en"},{"source":"CNA","value":"Kaixuan Li ","lang":"en"},{"source":"CNA","value":"Evan Zhou ","lang":"en"}],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"collectionURL":"https://repo.maven.apache.org/maven2","defaultStatus":"unaffected","packageName":"org.apache.kafka:kafka","packageURL":"pkg:maven/org.apache.kafka/kafka","product":"Apache Kafka","vendor":"Apache Software Foundation","versions":[{"lessThanOrEqual":"4.1.2","status":"affected","version":"4.1.0","versionType":"semver"},{"lessThanOrEqual":"4.2.1","status":"affected","version":"4.2.0","versionType":"semver"},{"status":"affected","version":"4.3.0","versionType":"semver"}]}],"credits":[{"lang":"en","type":"reporter","value":"San Zhang "},{"lang":"en","type":"reporter","value":"Kaixuan Li "},{"lang":"en","type":"remediation developer","value":"Evan Zhou "}],"descriptions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"
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). 
"}],"value":"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.\n\n\nImpact:\n\nA 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.\n\n\nMitigation (all affected versions, no upgrade required):\n\nSet sasl.oauthbearer.jwks.endpoint.url for every listener/mechanism that uses OAuthBearerValidatorCallbackHandler, or configure a signature-verifying sasl.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 non-verifying ClientJwtValidator fails to start with a ConfigException instead of running without signature verification (secure by default)."}],"metrics":[{"other":{"content":{"text":"important"},"type":"Textual description of severity"},"scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-345","description":"CWE-345 Insufficient Verification of Data Authenticity and its child","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-347","description":"CWE-347 Improper verification of cryptographic signature","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-1287","description":"CWE-1287 Improper validation of specified type of input","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-636","description":"CWE-636 Failing Open","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-10-28T16:37:45.688Z","orgId":"f0158376-9dc2-43b6-827c-5f631a4d8d09","shortName":"apache"},"references":[{"tags":["vendor-advisory"],"url":"https://kafka.apache.org/cve-list"}],"source":{"discovery":"EXTERNAL"},"title":"Apache Kafka: Broker silently skips JWT signature verification for SASL/OAUTHBEARER when the JWKS endpoint URL is not configured","x_generator":{"engine":"Vulnogram 1.0.3"}}},"cveMetadata":{"assignerOrgId":"f0158376-9dc2-43b6-827c-5f631a4d8d09","assignerShortName":"apache","cveId":"CVE-2026-110985","datePublished":"2026-10-28T16:37:45.688Z","dateReserved":"2026-10-15T11:31:31.708Z","dateUpdated":"2026-10-28T16:37:45.688Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-28 17:17:38","lastModifiedDate":"2026-10-28 17:17:38","problem_types":["CWE-345","CWE-347","CWE-636","CWE-1287","CWE-345 CWE-345 Insufficient Verification of Data Authenticity and its child","CWE-347 CWE-347 Improper verification of cryptographic signature","CWE-1287 CWE-1287 Improper validation of specified type of input","CWE-636 CWE-636 Failing Open"],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"110985","Ordinal":"1","Title":"Apache Kafka: Broker silently skips JWT signature verification f","CVE":"CVE-2026-110985","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"110985","Ordinal":"1","NoteData":"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.\n\n\nImpact:\n\nA 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.\n\n\nMitigation (all affected versions, no upgrade required):\n\nSet sasl.oauthbearer.jwks.endpoint.url for every listener/mechanism that uses OAuthBearerValidatorCallbackHandler, or configure a signature-verifying sasl.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 non-verifying ClientJwtValidator fails to start with a ConfigException instead of running without signature verification (secure by default).","Type":"Description","Title":"Apache Kafka: Broker silently skips JWT signature verification f"}]}}}