VDB
CVE-2026-59980
CVE-2026-59980
PUBLISHED
CVSS 6.3 MEDIUM
Reported by GitHub_M · Published September 23, 2026
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.
Risk Scores
CVSS 4.0
6.3
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
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| python-hyper | hpack | < 4.2.0 |
| PyPI | hpack | 0 |
| chainguard | airflow-2 | 0, 0 |
| python-hyper | hpack | < 4.2.0, < 4.2.0, < 4.2.0 |
| chainguard | authentik-2025.12 | 0, 0 |
Timeline
- Aug 19, 2026 CVE Published
- Sep 24, 2026 EPSS Score
- Sep 26, 2026 EPSS Score
- Sep 30, 2026 EPSS Score
- Sep 30, 2026 Security Advisory
- Oct 2, 2026 EPSS Score
- Oct 6, 2026 EPSS Score
References
- https://github.com/python-hyper/hpack/security/advisories/GHSA-8v8h-hg4w-mvq2 x_refsource_CONFIRM
- https://github.com/python-hyper/hpack/commit/8cfb02c547740e16dbfe7aba77bad84b297cec2c x_refsource_MISC
- https://cs.opensource.google/go/x/net/+/master:http2/hpack/hpack.go;l=468;drc=8e2b117aee74f6b86c207a808b0255de45c0a18a x_refsource_MISC
- https://docs.rs/http2/0.5.19/src/http2/hpack/decoder.rs.html#403 x_refsource_MISC
- https://nvd.nist.gov/vuln/detail/CVE-2026-59980 advisory
- https://github.com/advisories/GHSA-8v8h-hg4w-mvq2 advisory
- https://github.com/python-hyper/hpack/releases/tag/v4.2.0 url