Home/CVE/A possible security vulnerability has been identified in Apache Kafka. By default, the broker property `sasl.oauthbeare
CVE

CVE-2026-33557

A possible security vulnerability has been identified in Apache Kafka. By default, the broker property `sasl.oauthbeare

A possible security vulnerability has been identified in Apache Kafka. By default, the broker property sasl.oauthbearer.jwt.validator.class is set to org.apache.kafka.common.security.oauthbearer.DefaultJwtValidator. It accepts any JWT token without validating its signature, issuer, or audience.

An attacker can generate a JWT token from any issuer with the preferred_username set to any user, and the broker will accept it. We advise the Kafka users using kafka v4.1.0 or v4.1.1 to set the config sasl.oauthbearer.jwt.validator.class to org.apache.kafka.common.security.oauthbearer.BrokerJwtValidator explicitly to avoid this vulnerability. Since Kafka v4.1.2 and v4.2.0 and later, the issue is fixed and will correctly validate the JWT token.

CRITICAL · CVSS 9.1 EPSS 0.00223
Schedule remediation
  • SSVC automatable: yes - attacks can be scripted at scale
  • CVSS base score ≥ 7.0
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-1285Improper Validation of Specified Index, Position, or Offset in Input
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Affected Products & Versions

1
apache kafka>= 4.1.0 and < 4.1.2
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Affected Packages

1
Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.
Maven org.apache.kafka:kafka-clients CRITICAL fixed in 4.1.2
▣

Scoring & Timeline

9.1
CRITICAL · CVSS v3.1 · security@apache.org
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD20 Apr 2026 · 02:16 PM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
yes
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
⚑

Vendor Advisories

1
oracle-cpuoracle-cpu-Oracle-Communications-Unified-Assurance-14597--CVE-2026-33557
🔗

References & Sources

3
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://kafka.apache.org/cve-listVendor Advisory
https://lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953hMitigationVendor Advisory
http://www.openwall.com/lists/oss-security/2026/04/17/2Mailing List
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