GHSA-8v8h-hg4w-mvq2
hpack: Unbounded variable integer decoding can cause run-away computation on malformed input
Quick fix
GHSA-8v8h-hg4w-mvq2 — hpack: upgrade to the fixed version with the command below.
pip install --upgrade 'hpack>=4.2.0'Details
### Impact
Users of the python-hyper/hpack library, most commonly used as downstream dependency of the python-hyper/h2 library (an HTTP/2 client and server implementation). Unbounded variable integer decoding can cause run-away computation on malformed input leading to O(n^2) runtime, effectively blocking further processing with large enough unsanitized input.
### Patches A fix is available in python-hyper/hpack v4.2.0 to restricted variable integer decoding to uint32 to prevent run-away computation.
### Workarounds Sanitize input to hpack decoder for long sequences of `0xFF` values to prevent malicious use.
Are you affected?
Enter the version of the package you're using.
Affected packages
References
- https://github.com/python-hyper/hpack/security/advisories/GHSA-8v8h-hg4w-mvq2[WEB]
- https://nvd.nist.gov/vuln/detail/CVE-2026-59980[ADVISORY]
- https://github.com/python-hyper/hpack/commit/8cfb02c547740e16dbfe7aba77bad84b297cec2c[WEB]
- https://cs.opensource.google/go/x/net/+/master:http2/hpack/hpack.go;l=468;drc=8e2b117aee74f6b86c207a808b0255de45c0a18a[WEB]
- https://docs.rs/http2/0.5.19/src/http2/hpack/decoder.rs.html#403[WEB]
- https://github.com/python-hyper/hpack[PACKAGE]
- https://github.com/python-hyper/hpack/releases/tag/v4.2.0[WEB]