hpack: Unbounded variable integer decoding can cause run-away computation on malformed input

中 6.3CVE-2026-59980 · GHSA-8v8h-hg4w-mvq2 · PYSEC-2026-4053 · 23/09/2026 公開 · 30/09/2026 更新

要点

CVE-2026-59980 は hpack に影響する深刻度「中」 (CVSS 6.3) の脆弱性です。
今後30日間に悪用される確率（EPSS）：0.30%（全脆弱性の 22.9% より高い）。
対処：4.2.0 以降に更新してください。

パッケージ	影響を受けるバージョン	修正済みバージョン
hpack PyPI	`< 4.2.0`	`4.2.0`

概要

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.

NVD の説明

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.