{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-110952", "assignerOrgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09", "state": "PUBLISHED", "assignerShortName": "apache", "dateReserved": "2026-10-15T09:13:40.750Z", "datePublished": "2026-10-28T16:37:34.723Z", "dateUpdated": "2026-10-28T16:37:34.723Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09", "shortName": "apache", "dateUpdated": "2026-10-28T16:37:34.723Z"}, "title": "Apache Kafka: Broker does not enforce JWT issuer and audience validation for SASL/OAUTHBEARER by default", "problemTypes": [{"descriptions": [{"description": "CWE-345 Insufficient Verification of Data Authenticity)", "lang": "en", "cweId": "CWE-345", "type": "CWE"}]}, {"descriptions": [{"description": "CWE-1188 Initialization of a resource with an insecure default", "lang": "en", "cweId": "CWE-1188", "type": "CWE"}]}], "source": {"discovery": "EXTERNAL"}, "affected": [{"vendor": "Apache Software Foundation", "product": "Apache Kafka", "packageURL": "pkg:maven/org.apache.kafka/kafka", "versions": [{"status": "affected", "version": "3.1.0", "lessThan": "4.4.0", "versionType": "semver"}], "defaultStatus": "unaffected", "collectionURL": "https://repo.maven.apache.org/maven2", "packageName": "org.apache.kafka:kafka"}], "descriptions": [{"value": "A Kafka broker that authenticates clients with SASL/OAUTHBEARER using the bundled JWKS-backed validator always verifies the JWT signature, but two further checks are only performed when explicitly configured:\n\n- The issuer (iss) claim is verified only when sasl.oauthbearer.expected.issuer is set. When it is unset, a validly-signed token carrying the expected audience is accepted regardless of which issuer minted it.\n- An audience (aud) claim is required only when sasl.oauthbearer.expected.audience is set. When it is unset, a validly-signed token that omits the aud claim is accepted. (A token that carries an aud claim is\n still rejected when no expected audience is configured.)\n\nBoth options default to unset and have been documented as optional (Importance LOW) since KIP-768 (3.1.0).\n\nImpact:\n The exposure is realizable mainly in deployments whose JWKS endpoint serves signing keys for more than one issuer (a multi-tenant identity provider, an aggregated/shared JWKS, or shared signing keys): a token\n minted for a different issuer, or a token lacking an audience, may be accepted to authenticate \u2014 potentially as a higher-privileged principal. In a single-issuer deployment where the provider controls the iss\n claim and issues audience-scoped tokens, exposure is limited. The signature trust anchor remains enforced in all cases. This is distinct from CVE-2026-33557 (acceptance of unsigned/unvalidated tokens); here the\n signature is validated and only the issuer/audience checks are not enforced by default.\n\nMitigation (all affected versions, no upgrade required):\n Set both sasl.oauthbearer.expected.issuer (to your provider's exact iss value) and sasl.oauthbearer.expected.audience (to the audience(s) your brokers expect), per listener. Brokers that set these perform\n exact-match issuer/audience checks and are not affected. Both have been available since 3.1.0.\n\nResolution:\n - From Apache Kafka 4.4.0: a broker configured with a JWKS endpoint fails to start unless both sasl.oauthbearer.expected.issuer and sasl.oauthbearer.expected.audience are set (secure by default). Deployments that\n intentionally do not restrict the issuer and/or audience may opt out per axis with sasl.oauthbearer.allow.unverified.issuer=true and/or sasl.oauthbearer.allow.unverified.audience=true.", "lang": "en", "supportingMedia": [{"type": "text/html", "base64": false, "value": "<div></div><div><p>A Kafka broker that authenticates clients with SASL/OAUTHBEARER using the bundled JWKS-backed validator always verifies the JWT signature, but two further checks are only performed when explicitly configured:<br><br>- The issuer (iss) claim is verified only when sasl.oauthbearer.expected.issuer is set. When it is unset, a validly-signed token carrying the expected audience is accepted regardless of which issuer minted it.<br>- An audience (aud) claim is required only when sasl.oauthbearer.expected.audience is set. When it is unset, a validly-signed token that omits the aud claim is accepted. (A token that carries an aud claim is<br> still rejected when no expected audience is configured.)<br><br>Both options default to unset and have been documented as optional (Importance LOW) since KIP-768 (3.1.0).<br><br>Impact:<br> The exposure is realizable mainly in deployments whose JWKS endpoint serves signing keys for more than one issuer (a multi-tenant identity provider, an aggregated/shared JWKS, or shared signing keys): a token<br> minted for a different issuer, or a token lacking an audience, may be accepted to authenticate \u2014 potentially as a higher-privileged principal. In a single-issuer deployment where the provider controls the iss<br> claim and issues audience-scoped tokens, exposure is limited. The signature trust anchor remains enforced in all cases. This is distinct from CVE-2026-33557 (acceptance of unsigned/unvalidated tokens); here the<br> signature is validated and only the issuer/audience checks are not enforced by default.<br><br>Mitigation (all affected versions, no upgrade required):<br> Set both sasl.oauthbearer.expected.issuer (to your provider's exact iss value) and sasl.oauthbearer.expected.audience (to the audience(s) your brokers expect), per listener. Brokers that set these perform<br> exact-match issuer/audience checks and are not affected. Both have been available since 3.1.0.<br><br>Resolution:<br> - From Apache Kafka 4.4.0: a broker configured with a JWKS endpoint fails to start unless both sasl.oauthbearer.expected.issuer and sasl.oauthbearer.expected.audience are set (secure by default). Deployments that<br> intentionally do not restrict the issuer and/or audience may opt out per axis with sasl.oauthbearer.allow.unverified.issuer=true and/or sasl.oauthbearer.allow.unverified.audience=true.</p></div>"}]}], "references": [{"url": "https://kafka.apache.org/cve-list", "tags": ["vendor-advisory"]}], "metrics": [{"other": {"type": "Textual description of severity", "content": {"text": "moderate"}}, "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "credits": [{"lang": "en", "value": "Kai Aizen <[email protected]>, SnailSploit", "type": "reporter"}, {"lang": "en", "value": "Evan Zhou <[email protected]>", "type": "remediation developer"}], "x_generator": {"engine": "Vulnogram 1.0.3"}}}}

{}

{"affected": [{"affectedData": [{"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": [{"lessThan": "4.4.0", "status": "affected", "version": "3.1.0", "versionType": "semver"}]}], "source": "[email protected]"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "A Kafka broker that authenticates clients with SASL/OAUTHBEARER using the bundled JWKS-backed validator always verifies the JWT signature, but two further checks are only performed when explicitly configured:\n\n- The issuer (iss) claim is verified only when sasl.oauthbearer.expected.issuer is set. When it is unset, a validly-signed token carrying the expected audience is accepted regardless of which issuer minted it.\n- An audience (aud) claim is required only when sasl.oauthbearer.expected.audience is set. When it is unset, a validly-signed token that omits the aud claim is accepted. (A token that carries an aud claim is\n still rejected when no expected audience is configured.)\n\nBoth options default to unset and have been documented as optional (Importance LOW) since KIP-768 (3.1.0).\n\nImpact:\n The exposure is realizable mainly in deployments whose JWKS endpoint serves signing keys for more than one issuer (a multi-tenant identity provider, an aggregated/shared JWKS, or shared signing keys): a token\n minted for a different issuer, or a token lacking an audience, may be accepted to authenticate \u2014 potentially as a higher-privileged principal. In a single-issuer deployment where the provider controls the iss\n claim and issues audience-scoped tokens, exposure is limited. The signature trust anchor remains enforced in all cases. This is distinct from CVE-2026-33557 (acceptance of unsigned/unvalidated tokens); here the\n signature is validated and only the issuer/audience checks are not enforced by default.\n\nMitigation (all affected versions, no upgrade required):\n Set both sasl.oauthbearer.expected.issuer (to your provider's exact iss value) and sasl.oauthbearer.expected.audience (to the audience(s) your brokers expect), per listener. Brokers that set these perform\n exact-match issuer/audience checks and are not affected. Both have been available since 3.1.0.\n\nResolution:\n - From Apache Kafka 4.4.0: a broker configured with a JWKS endpoint fails to start unless both sasl.oauthbearer.expected.issuer and sasl.oauthbearer.expected.audience are set (secure by default). Deployments that\n intentionally do not restrict the issuer and/or audience may opt out per axis with sasl.oauthbearer.allow.unverified.issuer=true and/or sasl.oauthbearer.allow.unverified.audience=true."}], "id": "CVE-2026-110952", "lastModified": "2026-10-28T17:17:37.997", "metrics": {}, "published": "2026-10-28T17:17:37.997", "references": [{"source": "[email protected]", "url": "https://kafka.apache.org/cve-list"}], "sourceIdentifier": "[email protected]", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-345"}, {"lang": "en", "value": "CWE-1188"}], "source": "[email protected]", "type": "Primary"}]}

{}

{"created": "2026-10-28T17:30:15.427986+00:00", "updated": "2026-10-28T17:30:15.427992+00:00", "vendors": []}