GHSA-8v8h-hg4w-mvq2

Suggest an improvement
Source
https://github.com/advisories/GHSA-8v8h-hg4w-mvq2
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-8v8h-hg4w-mvq2/GHSA-8v8h-hg4w-mvq2.json
JSON Data
https://api.test.osv.dev/v1/vulns/GHSA-8v8h-hg4w-mvq2
Aliases
Downstream
CGA (2)
MINI (2)
Published
2026-09-24T19:43:26Z
Modified
2026-09-24T20:00:06Z
Severity
  • 6.3 (Medium) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N CVSS Calculator
Summary
hpack: Unbounded variable integer decoding can cause run-away computation on malformed input
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.

Database specific 
{
    "cwe_ids": [
        "CWE-400"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-24T19:43:26Z",
    "nvd_published_at": "2026-09-23T23:17:11Z",
    "severity": "MODERATE"
}
References

Affected packages

PyPI / hpack

Package

Name
hpack
View open source insights on deps.dev
Purl
pkg:pypi/hpack

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected
Fixed
4.2.0

Affected versions

1.*
1.0.0
1.0.1
1.1.0
2.*
2.0.0
2.0.1
2.1.0
2.1.1
2.2.0
2.3.0
3.*
3.0.0
4.*
4.0.0
4.1.0

Database specific

last_known_affected_version_range 
"<= 4.1.0"
source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-8v8h-hg4w-mvq2/GHSA-8v8h-hg4w-mvq2.json"