Allocation of Resources Without Limits or Throttling Affecting hpack package, versions [,4.2.0)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-PYTHON-HPACK-20074632
- published24 Sept 2026
- disclosed23 Sept 2026
- creditHiroki Nishino
Introduced: 23 Sep 2026
NewCVE-2026-59980 (opens in a new tab)How to fix?
Upgrade hpack to version 4.2.0 or higher.
Overview
Affected versions of this package are vulnerable to Allocation of Resources Without Limits or Throttling via the decode_integer function in src/hpack/hpack.py, where an attacker can send an HPACK-encoded integer with an unbounded number of continuation octets, causing run-away computation that crashes the decoder. The HPACK RFC 7541 Section 5.1 explicitly permits values of indefinite size and notes that encoders can send large numbers of zero values to waste octets or overflow integer values, and the library did not enforce any limit on the number of octets consumed during variable-length integer decoding.