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Fencer Intel
high 7.5

CVE-2026-111551 json

Apache Kafka: Denial of service in Kafka Streams and client deserializers via unbounded memory allocation

published 12d ago modified 4d ago also EUVD-2026-112172

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 42%
public exploits
0
none known

Summary

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.

Patch / fix

  • org.apache.kafka kafka-streams 4.2.2, 4.3.2
  • org.apache.kafka kafka-clients 4.2.2, 4.3.2
  • apache kafka 4.2.2, 4.3.2
  • org.apache.kafka kafka 4.2.2, 4.3.2

Is CVE-2026-111551 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-111551 updated cvss 7.5

org.apache.kafka/kafka-streams: org.apache.kafka/kafka-clients: Apache Kafka: Denial of Service via memory exhaustion during deserialization

  • Red Hat build of Apache Camel 4 for Quarkus 3 kafka-clients 4.1.2.redhat-00001 Red Hat build of Apache Camel for Spring Boot 4 kafka-clients 4.1.2.redhat-00001 Red Hat build of Apicurio Registry 3 kafka-clients 4.1.2.redhat-00001 Red Hat build of Debezium 3 kafka-clients 4.1.2.redhat-00001 Red Hat build of Quarkus kafka-clients 4.1.2.redhat-00001, kafka-streams 4.1.2.redhat-00001
    affected: workaround, no fix available
  • Red Hat Fuse 7 kafka-clients 4.1.2.redhat-00001, kafka-streams 4.1.2.redhat-00001
    affected: workaround, no fix available “Fix deferred”
  • Red Hat streams for Apache Kafka 3 kafka-clients 4.1.2.redhat-00001, kafka-streams 4.1.2.redhat-00001
    affected: workaround, no fix available
  • Red Hat OpenShift Serverless openshift-serverless-1/kn-ekb-receiver-rhel9, openshift-serverless-1/kn-ekb-dispatcher-rhel9
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
4d ago

Exploit prediction

0.50% chance of exploitation in the next 30 days, higher than 42% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Apache Software Foundation Apache Kafka

Classification

Weakness
  • CWE-789 Memory Allocation with Excessive Size Value
  • CWE-400 Uncontrolled Resource Consumption
  • CWE-20 Improper Input Validation

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.