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AIKIDO-2026-59285

http4k-core is vulnerable to Denial of Service (DoS)

Denial of Service (DoS)CVE-2026-53659 Published Aug 3, 2026

75

High Risk

This Affects:

JAVAhttp4k-core
2.17.0 - 4.48.2.0
Fixed in 4.51.0.0
5.0.0.0 - 5.41.0.0
Fixed in 5.42.0.0
6.0.0.0 - 6.48.0.0
Fixed in 6.49.0.0
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TL;DR

http4k-core decompresses incoming gzip-encoded request bodies through ServerFilters.GZip, RequestFilters.GunZip, and the underlying Gzip helpers without limiting the decompressed size. A small crafted request body of a few kilobytes can expand to gigabytes and exhaust the JVM heap. An unauthenticated client can trigger this against any server that accepts gzip-encoded requests, denying service to other clients. The fix caps decompression at a configurable default size, returning 413 Request Entity Too Large for oversized requests and throwing SizeLimitExceededException on other decompression paths.

Who does this affect?

You are affected if you are using a version that falls within the vulnerable range and your server decompresses incoming gzip-encoded request bodies via ServerFilters.GZip or RequestFilters.GunZip.

Background info

http4k-core is vulnerable to Denial of Service (DoS) in versions 2.17.0 - 4.48.2.0, 5.0.0.0 - 5.41.0.0 and 6.0.0.0 - 6.48.0.0.

How to fix this

Upgrade the org.http4k:http4k-core library to the patch version.

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