---
id: CVE-2026-53659
title: http4k is a functional toolkit for Kotlin HTTP applications
summary: >-
  http4k is a functional toolkit for Kotlin HTTP applications. Prior to
  4.51.0.0, 5.42.0.0, and 6.49.0.0, ServerFilters.GZip, RequestFilters.GunZip,
  and the underlying Gzip request-body decompression functions impose no limit
  on decompress…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-409
vendor: http4k
product: http4k
affected:
  - http4k < 4.51.0.0
  - 'http4k >= 5.0.0.0, < 5.42.0.0'
  - 'http4k >= 6.0.0.0, < 6.49.0.0'
patched:
  - 'org.http4k:http4k-core 5.42.0.0'
  - 'org.http4k:http4k-core 6.49.0.0'
published: '2026-09-14'
updated: '2026-09-14'
sourceUpdated: '2026-09-14T19:17:25.610'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-53659'
references:
  - url: >-
      https://github.com/http4k/http4k/commit/2618fe08f9801353012561ae1f1382fa2d37bac9
    label: security-advisories@github.com
  - url: >-
      https://github.com/http4k/http4k/commit/9f9e02f8efbbe04e0c70f1c46eef5d9d9067ea5b
    label: security-advisories@github.com
  - url: 'https://github.com/http4k/http4k/releases/tag/6.49.0.0'
    label: security-advisories@github.com
  - url: 'https://github.com/http4k/http4k/security/advisories/GHSA-g4w2-6h2r-3m3w'
    label: security-advisories@github.com
  - url: 'https://github.com/advisories/GHSA-g4w2-6h2r-3m3w'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53659.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-53659'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2533236'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-53659'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-53659'
tags:
  - nvd
  - cve.org
  - ghsa
  - maven
  - csaf
  - vex
  - red-hat
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-14T19:03:47.669547Z'
aliases:
  - GHSA-g4w2-6h2r-3m3w
ecosystem: maven
ingestedAt: '2026-08-17T22:01:17.029Z'
epss: 0.0063
epssPercentile: 0.47975
---

## Overview

http4k is a functional toolkit for Kotlin HTTP applications. Prior to 4.51.0.0, 5.42.0.0, and 6.49.0.0, ServerFilters.GZip, RequestFilters.GunZip, and the underlying Gzip request-body decompression functions impose no limit on decompressed size. An unauthenticated client can send a small gzip-encoded request body that expands to gigabytes, exhausting the JVM heap and denying service to other clients. The fix uses SizeLimitedInputStream to enforce a default 10 MiB limit, causes ServerFilters.GZip and RequestFilters.GunZip to return 413 Request Entity Too Large, and causes other decompression paths to throw SizeLimitExceededException. This issue is fixed in versions 4.51.0.0, 5.42.0.0, and 6.49.0.0.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-53659)

Affected packages:

- `org.http4k:http4k-core >= 5.0.0.0, < 5.42.0.0`
- `org.http4k:http4k-core <= 4.48.2.0`
- `org.http4k:http4k-core >= 6.0.0.0, < 6.49.0.0`

Patched in:

- `org.http4k:http4k-core 5.42.0.0`
- `org.http4k:http4k-core 6.49.0.0`

Source: https://github.com/advisories/GHSA-g4w2-6h2r-3m3w

## Vendor advisories

- **Red Hat VEX** · Important · updated 2026-09-18 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53659.json)