CVE-2026-111115: Apache Kafka: Broker OutOfMemoryError via tagged-field allocation amplification in flexible protocol request parsing

Awaiting analysis
Published 28-10-2026Last modified 28-10-2026

Vulnerability summary

CVE-2026-111115 is a vulnerability in apache software foundation apache kafka with no CVSS score yet. EPSS estimates a 0.24% chance of exploitation in the next 30 days, higher than 14.6% of scored vulnerabilities.

Priority
Insufficient evidence

No CVSS vector published; no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
Not scored
010
No CVSS score recorded
EPSS score
0.24%
0%100%
Low · Change unavailable
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Timeline

  1. 28-10-2026
    PublishedVulnerability first disclosed.
  2. 28-10-2026
    Last modifiedVulnerability information updated.

Description

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.

CVSS metrics

Risk metrics not yet published.

EPSS trend

Probability

0.24%

Chance of exploitation in the next 30 days

Percentile

15%

Versus all other CVEs

30-day change

Change unavailable

Change unavailable

29-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

No weakness data has been published for this record.

Affected systems

Version check

Known conditions: not stated in public data.

Apache software foundation1 product
  • apache kafka≥ 2.4.0, ≤ 4.1.2 | ≥ 4.2.0, ≤ 4.2.1 | ≥ 4.3.0, ≤ 4.3.1

1 vendor · 1 product

References

2 links