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No exploitation reportedAwaiting NVD analysis

CVE-2026-110985

Apache Kafka: Broker silently skips JWT signature verification for SASL/OAUTHBEARER when the JWKS endpoint URL is not configured

No exploitation reported by the sources we read.

  • Published2026-10-28
  • WeaknessCWE-1287 · CWE-345 · CWE-347

Am I affected?

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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. 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).

Timeline

dates in UTC
  1. 2026-10-2816:37CVE publishedCNA

Versions per branch

Products declared by the CNA1 product

As apache, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • Apache Software Foundation Apache Kafkaother versions: not affected

    package org.apache.kafka:kafkahttps://repo.maven.apache.org/maven2

    Affected
    • ≥ 4.1.0, ≤ 4.1.2no fix statedsemver
    • ≥ 4.2.0, ≤ 4.2.1no fix statedsemver
    • = 4.3.0no fix statedsemver

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-10-28

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • kafkaUbuntu:Pro:18.04:LTSall versions · no fixed version listed

Vendor advisories

  • CVE-2026-110985 Red Hat Product Security

    org.apache.kafka/kafka-clients: Apache Kafka: Authentication bypass via missing JWT signature verification

Full record on NVD

Fix

No fix published by the sources we read yet. NVD record

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • CISA-ADPSSVC decisionnone2026-11-05
  • CISA-ADPCVSS 3.19.12026-11-05
  • CNAweakness (CWE)CWE-1287, CWE-345, CWE-347, CWE-6362026-10-28
  • NVDweakness (CWE)CWE-1287, CWE-345, CWE-347, CWE-636read 2026-11-05
  • FIRST EPSSEPSS score0.1 %2026-11-05
  • OSVaffected packages—
  • GitHub Advisoriesadvisory—

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Published
2026-10-28
Last Modified
2026-11-05
NVD status
Awaiting Analysis
GitHub Advisory
GHSA-j27v-m9ww-p89m

Frequently asked questions

What is CVE-2026-110985?

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).

Is CVE-2026-110985 actively exploited?

Active exploitation of CVE-2026-110985 has not been confirmed. Its EPSS score was 0.1% on 2026-11-05, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-110985?

CVE-2026-110985 has a CVSS v3 base score of 9.1 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

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