CVE-2026-33557 — Improper Validation of Specified Index, Position, or Offset in Input in Software Foundation Apache Kafka

CWE-1285 — Improper Validation of Specified Index, Position, or Offset in InputCWE-303 — Incorrect Implementation of Authentication Algorithm6 documents6 sources
Severity
9.1CRITICALNVD
EPSS
0.2%
top 58.09%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
5
Apache Software Foundation Apache KafkaApache Log4jLog4j 2 Log4j+2 more
Timeline
PublishedApr 20

Description

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 c…

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:NExploitability: 3.9 | Impact: 5.2

Affected Packages5 packages

▶CVEListV5apache_software_foundation/apache_kafka4.1.0 — 4.1.1
▶Red Hatapache/log4j
▶Red Hatlog4j_2/log4j

🔴Vulnerability Details

3
GHSA
Apache Kafka does not validate JWT tokens in its OAUTHBEARER authentication implementation↗2026-04-20
▶
GHSA
GHSA-28jg-cgg7-j4wc: A possible security vulnerability has been identified in Apache Kafka↗2026-04-20
▶
VulDB
Apache Kafka 4.1.0 JWT Token improper authentication↗2026-04-17
▶

📋Vendor Advisories

1
Red Hat
kafka: Apache Kafka: Authentication bypass via improper JWT validation↗2026-04-20
▶

💬Community

1
Bugzilla
CVE-2026-33557 kafka: Apache Kafka: Authentication bypass via improper JWT validation↗2026-04-20
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