Bug 2562994 (CVE-2026-111551)

Summary: CVE-2026-111551 org.apache.kafka/kafka-streams: org.apache.kafka/kafka-clients: Apache Kafka: Denial of Service via memory exhaustion during deserialization
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: ant, asyoung, ccranfor, cescoffi, chfoley, cmah, dhanak, drosa, dsimansk, ewittman, fmariani, fmongiar, gmalinko, gsmet, gtanzill, janstey, jbuscemi, jhollowa, jmartisk, jnethert, jpechane, jturenov, jwon, kaycoth, kingland, manderse, mcarlett, mnovotny, nipatil, olubyans, ozzy, pantinor, pdelbell, pjindal, prichard, rguimara, rhel-process-autobot, rkubis, rstepani, sausingh, sbiarozk, sthirugn, swoodman, tcunning, varjain, watson-tool-maintainers, yfang
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Apache Kafka. Several deserialization routines in the client and Streams libraries allocate memory directly based on an input's declared size field without validating whether enough data is actually available. An attacker who can send crafted messages to affected topics or consumer groups can specify an excessively large size to trigger massive memory allocations. This condition can exhaust system memory, resulting in a Denial of Service (DoS) by crashing the affected consumer application or processing thread.
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Description OSIDB Bzimport 2026-10-28 17:15:14 UTC 
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.