---
cve: "CVE-2026-47066"
severity: "HIGH"
cvss: 8.7
epss: "75%"
vendor: "benoitc"
kev: false
exploited: false
published: "2026-05-25 15:16:21"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-14T18:31:36+02:00"
---

# CVE-2026-47066

> 8.7 HIGH · 🧪 PoC

## Beschreibung

Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in benoitc hackney allows Excessive Allocation. The Alt-Svc response header parser in src/hackney_altsvc.erl does not guarantee forward progress. When parse_token/2 receives a non-token, non-whitespace, non-comma byte (e.g. !, @, =, ;), it returns the input unchanged. skip_comma/1 also returns the buffer unchanged when the first byte is not a comma. parse_entries/2 then recurses with identical data, creating a tight infinite tail-recursive loop that pins a scheduler at 100% CPU. The calling process never returns.

The entry point parse_and_cache/3 is called synchronously in the connection process on every HTTP response. A single-byte Alt-Svc: ! response header is sufficient to trigger the hang; the header is fully controlled by any HTTP origin the client connects to.

This issue affects hackney: from 2.0.0-beta.1 before 4.0.1.

## CVSS-Vektor

```
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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)

- c41c8d48ace8141b003f6f1de3ca6734a0c53056 (Commit)
- e548aba1f97ffa3f4750da7b772998fb78c01894 (Commit)

## Referenzen

- <https://github.com/benoitc/hackney/security/advisories/GHSA-6cp8-v795-jr2j>
- <https://cna.erlef.org/cves/CVE-2026-47066.html>
- <https://osv.dev/vulnerability/EEF-CVE-2026-47066>
- <https://github.com/benoitc/hackney/commit/e548aba1f97ffa3f4750da7b772998fb78c01894>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-47066) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_