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Fencer Intel
critical 9.1

CVE-2026-111108 json

Apache Kafka: Broker OutOfMemoryError via array allocation amplification in code-generated protocol readers

published 12d ago modified 4d ago also EUVD-2026-112169

cvss
9.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 48%
public exploits
0
none known

Summary

Apache Kafka's code-generated protocol readers pre-size an array's collection from the element count declared by the sender. That count is checked only against the bytes remaining in the request buffer, which assumes about one byte per element; because most elements need several bytes, a request can declare far more elements than the buffer holds and still pass. For a keyed array the reader then allocates an ImplicitLinkedHashCollection of capacity (2 * count +1), so a request of a few tens of megabytes can force a heap allocation several times larger before any element is read. The pattern is emitted into every generated reader, so it affects all Kafka API types with an array field.

Impact:

Request parsing happens before any authorization check. On a listener that does not require authentication (for example PLAINTEXT), an unauthenticated attacker can send a few concurrent requests that each declare a very large=

array length and allocate many times their wire size in broker heap, crashing the broker with an OutOfMemoryError. The reporter demonstrated three concurrent ~90 MB ProduceRequest (v3) connections exhausting a 1 GB heap (~8x amplification). On listeners that require authentication, the attacker needs valid credentials but no specific ACL, since parsing precedes authorization..

Mitigation:

Upgrade to Apache Kafka 4.2.2, 4.3.2, or 4.4.0. Until then, lowering socket.request.max.bytes and restricting network access to broker listeners reduces, but does not remove, exposure.

Resolution:

From Apache Kafka 4.2.2, 4.3.2, and 4.4.0: generated readers cap the initial array pre-allocation at MessageUtil.MAX_PREALLOCATED_ARRAY_CAPACITY (1000) and grow it on demand, and reject a declared array length above MessageUtil.MAX_ARRAY_LENGTH (1,000,000).

Patch / fix

  • apache kafka 4.2.2, 4.3.2
  • org.apache.kafka kafka 4.2.2, 4.3.2

Is CVE-2026-111108 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-2026-111108 updated cvss 7.5

org.apache.kafka/kafka-clients: Apache kafka: Denial of Service via excessive memory allocation during request parsing

  • Red Hat streams for Apache Kafka 3 kafka-clients 4.1.2.redhat-00001
    affected: workaround, no fix available “Red Hat is not aware of any available mitigation for this issue. Customers are advised to apply the relevant security updates as they become available.”
  • Red Hat OpenShift Serverless openshift-serverless-1/kn-ekb-receiver-rhel9, openshift-serverless-1/kn-ekb-dispatcher-rhel9 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
    +1 more products
    Red Hat Fuse 7 kafka-clients 4.1.2.redhat-00001
    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

0.59% chance of exploitation in the next 30 days, higher than 48% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CISA ADP 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
CNA 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Affected products

  • Apache Software Foundation Apache Kafka

Classification

Weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling
  • CWE-789 Memory Allocation with Excessive Size Value
  • CWE-400 Uncontrolled Resource Consumption

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.