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GHSA-g4w2-6h2r-3m3w
org.http4k/http4k-coreorg.http4k/http4k-coreorg.http4k/http4k-coreImpact
ServerFilters.GZip and RequestFilters.GunZip (and the underlying Gzip functions used to decompress request bodies) did not impose any cap on the decompressed size. A small malicious gzip-encoded request body (on the order of kilobytes) could decompress to gigabytes, exhausting the JVM heap and denying service to other clients.
Who is affected: any http4k server that accepts gzip-encoded requests via ServerFilters.GZip or RequestFilters.GunZip. Exploitable by any unauthenticated client. The vulnerability was introduced on 2017-08-01 (commit 2618fe08f9) and was present for ~9 years.
Patches
| Line | Fixed in | Edition | |------|----------|---------| | v6.x (Community) | 6.49.0.0 | Community | | v5.x (LTS) | 5.42.0.0 | Enterprise — contact enterprise@http4k.org | | v4.x (LTS) | 4.51.0.0 | Enterprise — contact enterprise@http4k.org |
The fix caps decompression at 10MB by default; oversized requests through ServerFilters.GZip / RequestFilters.GunZip now return 413 Request Entity Too Large, and decompressing elsewhere throws SizeLimitExceededException. The keyed hmacSHA256 helper and other safe paths are unaffected.
Workarounds
For deployments that cannot upgrade immediately:
- Replace the
GZip/GunZipfilters with custom versions that wrap the decompressedInputStreamin a size-limited reader, or - Strip gzip-encoded request support at the edge (CDN, reverse proxy, or load balancer).
References
- Vulnerability introduced:
2618fe08f9 - Fix release: v6.49.0.0
- Background: CWE-409 — Improper Handling of Highly Compressed Data
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The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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