CVE-2026-53659http4k: Unbounded gzip decompression in `ServerFilters.GZip` / `RequestFilters.GunZip` allowed memory-exhaustion DoS
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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.
- CVSS
- 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-409
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Deferred
- Record last updated
- Sep 14, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
http4k http4k http4k:http4k (from the name) | before 4.51.0.0; from 5.0.0.0, < 5.42.0.0; from 6.0.0.0, < 6.49.0.0 | CNA record |
References
- https://github.com/http4k/http4k/security/advisories/GHSA-g4w2-6h2r-3m3wx-refsource-confirm
- https://github.com/http4k/http4k/commit/2618fe08f9801353012561ae1f1382fa2d37bac9x-refsource-misc
- https://github.com/http4k/http4k/commit/9f9e02f8efbbe04e0c70f1c46eef5d9d9067ea5bx-refsource-misc
- https://github.com/http4k/http4k/releases/tag/6.49.0.0x-refsource-misc
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.