---
cve: "CVE-2026-59980"
severity: "MEDIUM"
cvss: 6.3
epss: "5.3%"
vendor: "python-hyper"
kev: false
exploited: false
published: "2026-09-23 23:17:11"
tags: [cve, security, medium]
source: tsecurity.de CVE-Dossier
exported: "2026-09-24T20:36:02+02:00"
---

# CVE-2026-59980

> 6.3 MEDIUM · 🧪 PoC

## Beschreibung

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.

## CVSS-Vektor

```
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
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |

## Patch verfügbar (OSV)

- d05cff4cd462658847f67c48700aab40b2ba8cf1 (Commit)

## Referenzen

- <https://github.com/python-hyper/hpack/security/advisories/GHSA-8v8h-hg4w-mvq2>
- <https://github.com/python-hyper/hpack/commit/8cfb02c547740e16dbfe7aba77bad84b297cec2c>
- <https://cs.opensource.google/go/x/net/+/master:http2/hpack/hpack.go;l=468;drc=8e2b117aee74f6b86c207a808b0255de45c0a18a>
- <https://docs.rs/http2/0.5.19/src/http2/hpack/decoder.rs.html#403>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-59980) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_