CVE-2026-110952
Apache Kafka: Broker does not enforce JWT issuer and audience validation for SASL/OAUTHBEARER by default
Description
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: - 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. - 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 still rejected when no expected audience is configured.) Both options default to unset and have been documented as optional (Importance LOW) since KIP-768 (3.1.0). Impact: 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 minted for a different issuer, or a token lacking an audience, may be accepted to authenticate — potentially as a higher-privileged principal. In a single-issuer deployment where the provider controls the iss 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 signature is validated and only the issuer/audience checks are not enforced by default. Mitigation (all affected versions, no upgrade required): 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 exact-match issuer/audience checks and are not affected. Both have been available since 3.1.0. Resolution: - 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 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.
INFO
Published Date :
Oct. 28, 2026, 5:17 p.m.
Last Modified :
Nov. 5, 2026, 7:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | 134c704f-9b21-4f2e-91b3-4a467353bcc0 |
Solution
- Set sasl.oauthbearer.expected.issuer to the correct issuer value.
- Set sasl.oauthbearer.expected.audience to the expected audience(s).
- Update Kafka to version 4.4.0 or later.
- Configure opt-out settings if unverified issuer/audience is intended.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-110952.
| URL | Resource |
|---|---|
| https://kafka.apache.org/cve-list |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-110952 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-110952
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-110952 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-110952 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Nov. 05, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N Added SSVC {'id': 'CVE-2026-110952', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-11-05T19:06:04.222838Z'} -
New CVE Received by [email protected]
Oct. 28, 2026
Action Type Old Value New Value Added Description 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: - 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. - 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 still rejected when no expected audience is configured.) Both options default to unset and have been documented as optional (Importance LOW) since KIP-768 (3.1.0). Impact: 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 minted for a different issuer, or a token lacking an audience, may be accepted to authenticate — potentially as a higher-privileged principal. In a single-issuer deployment where the provider controls the iss 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 signature is validated and only the issuer/audience checks are not enforced by default. Mitigation (all affected versions, no upgrade required): 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 exact-match issuer/audience checks and are not affected. Both have been available since 3.1.0. Resolution: - 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 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. Added CWE CWE-345 Added CWE CWE-1188 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/110xxx/CVE-2026-110952.json">CVE-2026-110952</a> Added Reference https://kafka.apache.org/cve-list