[ CVE-2026-111115 · Published 28 Oct 2026 ]
Vulnerability in Apache Software Foundation Apache Kafka
[ Description ]Official 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.
[ Fixes ]Fixes and patches
No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.
[ Advisories ]Government CERT advisories
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CERT-FRCERTFR-2026-AVI-1415
Multiple vulnerabilities in Apache Kafka Translated from French
Multiple vulnerabilities have been discovered in Apache Kafka. Some of them allow an attacker to cause remote denial of service, a breach of data confidentiality and a breach of data integrity.
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BSI CERT-BundWID-SEC-2026-4221
Apache Kafka: Multiple vulnerabilities Translated from German