Vulnerability-Lookup

GHSA-J27V-M9WW-P89M

Vulnerability from github – Published: 2026-10-28 18:32 – Updated: 2026-10-28 18:32

Details

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).

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{
  "affected": [],
  "aliases": [
    "CVE-2026-110985"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-345"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-28T17:17:38Z",
    "severity": null
  },
  "details": "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).",
  "id": "GHSA-j27v-m9ww-p89m",
  "modified": "2026-10-28T18:32:03Z",
  "published": "2026-10-28T18:32:03Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-110985"
    },
    {
      "type": "WEB",
      "url": "https://kafka.apache.org/cve-list"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

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

Vulnerability from cvelistv5 – Published: 2026-10-28 16:37 – Updated: 2026-10-28 16:37

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

1 reference

URL	Tags
https://kafka.apache.org/cve-list	vendor-advisory

Impacted products

1 product

Vendor	Product	Version
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)

Credits

San Zhang <falaxe1642@gmail.com> Kaixuan Li <kaixuanli0131@gmail.com> Evan Zhou <ezhou@confluent.io>

Show details on NVD website

JSON

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Sightings

Author	Source	Type	Date	Other

Nomenclature

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Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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