Vulnerability Description
hpack is an HTTP/2 Header Encoding for Python. Prior to version 4.2.0, 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. A fix is available in python-hyper/hpack v4.2.0 to restricted variable integer decoding to uint32 to prevent run-away computation. As a workaround, sanitize input to hpack decoder for long sequences of `0xFF` values to prevent malicious use.
Related Weaknesses (CWE)
References
- https://cs.opensource.google/go/x/net/+/master:http2/hpack/hpack.go;l=468;drc=8e
- https://docs.rs/http2/0.5.19/src/http2/hpack/decoder.rs.html#403
- https://github.com/python-hyper/hpack/commit/8cfb02c547740e16dbfe7aba77bad84b297
- https://github.com/python-hyper/hpack/security/advisories/GHSA-8v8h-hg4w-mvq2
FAQ
What is CVE-2026-59980?
CVE-2026-59980 is a documented vulnerability. hpack is an HTTP/2 Header Encoding for Python. Prior to version 4.2.0, unbounded variable integer decoding can cause run-away computation on malformed input leading to O(n^2) runtime, effectively bloc...
How severe is CVE-2026-59980?
CVSS scoring is not yet available for CVE-2026-59980. Check NVD for updates.
Is there a patch for CVE-2026-59980?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.