Apache Kafka up to 4.1.2/4.2.1/4.3.0 PushTelemetry API ClientTelemetryUtils.decompress heap-based overflow

Summaryinfo

A vulnerability labeled as problematic has been found in Apache Kafka up to 4.1.2/4.2.1/4.3.0. Affected by this vulnerability is the function ClientTelemetryUtils.decompress of the component PushTelemetry API. Executing a manipulation can lead to heap-based overflow. This vulnerability is tracked as CVE-2026-111073. The attack can be launched remotely. No exploit exists. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as problematic was found in Apache Kafka up to 4.1.2/4.2.1/4.3.0. This vulnerability affects the function ClientTelemetryUtils.decompress of the component PushTelemetry API. The manipulation with an unknown input leads to a heap-based overflow vulnerability. The CWE definition for the vulnerability is CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). As an impact it is known to affect availability. CVE summarizes:

The broker-side PushTelemetry API (KIP-714) validates only the compressed size of a client's metrics payload against telemetry.max.bytes (default 1 MB) before decompressing it. ClientTelemetryUtils.decompress() then decompresses the payload with no limit on the decompressed output size, growing a heap buffer until the compressed input is exhausted. A small, highly compressible payload (for example gzip-compressed zeros) can therefore expand to hundreds of megabytes of broker heap. Impact: An authenticated client can send a PushTelemetry request with a small compressed payload that decompresses to a very large size, consuming broker heap out of proportion to the request size. Repeated or concurrent requests can exhaust the broker heap and cause an OutOfMemoryError, degrading or crashing the broker; a client that targets multiple brokers can affect cluster availability. PushTelemetry is available to any authenticated client and is not gated by an ACL. Mitigation: Upgrade to Apache Kafka 4.2.2, 4.3.1, or 4.4.0. On affected versions there is no configuration that fully prevents the amplification, because telemetry.max.bytes bounds only the compressed size; lowering telemetry.max.bytes reduces the worst-case decompressed size proportionally and is a partial mitigation. Resolution: - From Apache Kafka 4.2.2, 4.3.1, and 4.4.0: ClientTelemetryUtils.decompress() enforces a maximum decompressed size equal to telemetry.max.bytes (default 1 MB). Decompression reads in bounded chunks and aborts with a TelemetryTooLargeException once the decompressed total exceeds the limit, so an over-large or highly compressible payload is rejected instead of being fully expanded in heap. The decompressed size is therefore bounded by default.

The advisory is shared for download at kafka.apache.org. This vulnerability was named CVE-2026-111073 since 10/15/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 10/28/2026).

Upgrading to version 4.2.2, 4.3.1 or 4.4.0 eliminates this vulnerability.

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Productinfo

Vendor

• Apache

Name

• Kafka

Version

• 4.0
• 4.1
• 4.1.0
• 4.1.1
• 4.1.2
• 4.2
• 4.2.0
• 4.2.1
• 4.3.0

License

• open-source

Website

• Vendor: https://www.apache.org/

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