Open-Source Security Intelligence

Know every vulnerability
before it knows you.

DevGuard continuously monitors your dependencies and alerts you when CVEs like this one affect your stack — with real-time threat intelligence built for developers.

Checkout DevGuardView on GitHub
Search

GHSA-g4w2-6h2r-3m3w

HighCVSS 7.5 / 10
Published Aug 17, 2026·Last modified Aug 17, 2026
Affected Components(812)
Maven logoorg.http4k/http4k-core
4.31.0.0
Maven logoorg.http4k/http4k-core
1.31.0
Maven logoorg.http4k/http4k-core
4.22.0.1
1 / 271
Description

Impact

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 / GunZip filters with custom versions that wrap the decompressed InputStream in a size-limited reader, or
  • Strip gzip-encoded request support at the edge (CDN, reverse proxy, or load balancer).

References

Risk Scores
Base Score
7.5

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.

Threat Intelligence
6.9

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
N/A

Probability that this vulnerability will be exploited in the wild within the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

Related Vulnerabilities
  • CVE-2026-53659
    Alias

Browse More

High severity
Scan your project

Continuously monitor your dependencies and get alerted when vulnerabilities like this one affect your stack.

Checkout DevGuard