Apache Kafka: Improper Validation of Specified Index, Position, or Offset in Input
CVE-2026-33557 is a high-severity improper validation of specified index, position, or offset in input vulnerability in Apache Kafka from Apache, with a CVSS 3.1 base score of 8.6 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Apache Kafka versions: 4.1.0 through 4.1.1. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.9% chance of exploitation within 30 days, higher than 60% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Kafka to 4.1.2 or a later version.
- Read the advisory on kafka.apache.org for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Apache | Apache Kafka | 4.1.0 through 4.1.1 | Not stated |
| Red Hat | OpenShift Serverless | Not specified in the record | Not stated |
| Red Hat | Red Hat build of Apache Camel 4 for Quarkus 3 | Not specified in the record | Not stated |
| Red Hat | Red Hat build of Apache Camel for Spring Boot 4 | Not specified in the record | Not stated |
| Red Hat | Red Hat build of Apicurio Registry 2 | Not specified in the record | Not stated |
| Red Hat | Red Hat build of Apicurio Registry 3 | Not specified in the record | Not stated |
| Red Hat | Red Hat build of Debezium 2 | Not specified in the record | Not stated |
| Red Hat | Red Hat build of Debezium 3 | Not specified in the record | Not stated |
| Red Hat | Red Hat build of Quarkus | Not specified in the record | Not stated |
| Red Hat | Red Hat Data Grid 8 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 9 | Not specified in the record | Not stated |
| Red Hat | Red Hat Fuse 7 | Not specified in the record | Not stated |
| Red Hat | Red Hat JBoss Enterprise Application Platform 7 | Not specified in the record | Not stated |
| Red Hat | Red Hat JBoss Enterprise Application Platform 8 | Not specified in the record | Not stated |
| Red Hat | Red Hat JBoss Enterprise Application Platform Expansion Pack | Not specified in the record | Not stated |
| Red Hat | Red Hat Process Automation 7 | Not specified in the record | Not stated |
| Red Hat | streams for Apache Kafka 2 | Not specified in the record | Not stated |
| Red Hat | streams for Apache Kafka 3 | Not specified in the record | Not stated |
| Apache | Kafka | 4.1.0 up to, but not including, 4.1.2 | 4.1.2 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- LowLimited modification of data is possible.
- Availability
- LowPerformance or availability is reduced.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L. Scored by CNA.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.1 | Critical | CISA (ADP) |
| CVSS 3.1 | 8.6 | High | CNA |
Official 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 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Validation of Specified Index, Position, or Offset in Input
The product receives input that is expected to specify an index, position, or offset into an indexable resource such as a buffer or file, but it does not validate or incorrectly validates that the specified index/position/offset has the required properties.
More Improper Validation of Specified Index, Position, or Offset in Input vulnerabilities (CWE-1285)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other references
Other vulnerabilities in Apache Kafka
- 8.1 High severity
- 8.8 High severity
- 7.5 High severity
- 9.1 Critical severity
- 9.1 Critical severity
- 9.1 Critical severity
Recent Improper Validation of Specified Index, Position, or Offset in Input vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 9.1 Critical severity
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