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Fencer Vulns
critical 9.1

CVE-2026-111115 json

Apache Kafka: Broker OutOfMemoryError via tagged-field allocation amplification in flexible protocol request parsing

published 2026-10-28 11 d ago modified 2026-11-05 3 d ago also EUVD-2026-112170

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 46%
public exploits
0
none known

Summary

Apache Kafka's code-generated readers for flexible protocol versions read a tagged-field count declared by the sender and retain a RawTaggedField object for each unknown field. That count was bounded only by the outer request frame size (socket.request.max.bytes); it was not checked against the remaining buffer bytes or capped. Because each entry can be encoded in as little as two bytes (unknown tag 0, size 0), a modest request can declare tens of millions of tagged fields and force one object allocation per declared field. Flexible request headers (header version 2, used by flexible APIs such as ApiVersions v3) are parsed this way, so the amplification applies to the request header itself.

Impact: The flexible request header is parsed on the network thread before authorization, request dispatch, and request-time quota accounting. A client can send a request of a few tens of megabytes whose header declares about 20 million tagged fields, forcing roughly that many RawTaggedField allocations and exhausting broker heap or inducing process-wide GC stalls, denying broker service. Because the header is parsed for pre-authentication APIs such as ApiVersions (v3), the allocation can occur before authentication; no Kafka resource ACL or quota is required.

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 bounds-check the tagged-field count for flexible-versioned messages, rejecting a negative count, a count exceeding the remaining buffer bytes, or a count exceeding a fixed maximum (10,000), before any per-field allocation.

Patch / fix

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

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-2026-111115 updated cvss 7.5

org.apache.kafka/kafka-clients: Apache Kafka: Denial of Service via uncontrolled memory allocation in flexible request headers

  • 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
    affected: workaround, no fix available
  • Red Hat Fuse 7 kafka-clients 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
    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
3 d ago

Exploit prediction

0.56% chance of exploitation in the next 30 days, higher than 46% of all scored CVEs (FIRST EPSS, 2026-11-08).

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

References

Sources

Fencer Vulns 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.