Apache Kafka up to 4.1.2/4.2.1/4.3.1 ProcessorRecordContext allocation of resources

Summaryinfo

A vulnerability described as problematic has been identified in Apache Kafka up to 4.1.2/4.2.1/4.3.1. This affects an unknown function of the component ProcessorRecordContext/ChangedDeserializer/CombinedKeySchema/ProcessorMetadata/AssignmentInfo/ListDeserializer. Executing a manipulation can lead to allocation of resources. This vulnerability is tracked as CVE-2026-111551. The attack can be launched remotely. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability has been found in Apache Kafka up to 4.1.2/4.2.1/4.3.1 and classified as problematic. This vulnerability affects an unknown code block of the component ProcessorRecordContext/ChangedDeserializer/CombinedKeySchema/ProcessorMetadata/AssignmentInfo/ListDeserializer. The manipulation with an unknown input leads to a allocation of resources vulnerability. The CWE definition for the vulnerability is CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. As an impact it is known to affect availability. CVE summarizes:

Several Kafka deserialization paths read a size or count field from input data and use it directly to allocate an array, collection, or byte buffer, with no check against the bytes actually available. A small crafted input can therefore declare a very large size and force a multi-gigabyte allocation. The affected paths are, in Kafka Streams, ProcessorRecordContext (header count), ChangedDeserializer (varint value length), CombinedKeySchema (foreign-key length, which could also produce a negative size), ProcessorMetadata (key length), and AssignmentInfo group-assignment decoding; and, in the clients library, ListDeserializer (used by ListSerde). Impact: An attacker can trigger the oversized allocation and raise an OutOfMemoryError that crashes the affected consumer or Kafka Streams thread; the broker and the rest of the cluster are unaffected. The reachable surface depends on the path: writing a crafted record to a Streams application's internal changelog or repartition topics, or committing crafted offset metadata to its consumer group (Streams internal paths); writing a crafted record to any topic that a consumer reads with ListSerde (ListDeserializer); or, as a member of a Streams consumer group, returning crafted assignment data when elected leader (AssignmentInfo). Because a crafted record remains in its topic, the error can recur on restart. The record size limit (max.message.bytes) does not help, because the allocation is driven by a size field rather than by the input's length. Mitigation: Upgrade to Apache Kafka 4.2.2, 4.3.2, or 4.4.0. Where authorization is enabled, restrict write access to each application's internal topics and consumer group to its own principal, and restrict who can produce to topics that are consumed with ListSerde. Resolution: From Apache Kafka 4.2.2, 4.3.2, and 4.4.0: these deserialization paths validate the declared size against the remaining input before allocating and reject input that fails the check.

The advisory is available at kafka.apache.org. This vulnerability was named CVE-2026-111551 since 10/16/2026. The exploitation appears to be easy. The attack can be initiated remotely. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 10/28/2026). This vulnerability is assigned to T1499 by the MITRE ATT&CK project.

Upgrading to version 4.2.2, 4.3.2 or 4.4.0 eliminates this vulnerability.

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Productinfo

Vendor

• Apache

Name

• Kafka

Version

• 4.1.0
• 4.1.1
• 4.1.2
• 4.2.0
• 4.2.1
• 4.3.0
• 4.3.1

License

• open-source

Website

• Vendor: https://www.apache.org/

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