---
cve: "CVE-2026-97688"
severity: "MEDIUM"
cvss: 6.9
epss: "0.3%"
vendor: "urllib3"
kev: false
exploited: false
published: "2026-09-29 16:17:18"
tags: [cve, security, medium]
source: tsecurity.de CVE-Dossier
exported: "2026-10-24T09:14:15+02:00"
---

# CVE-2026-97688

> 6.9 MEDIUM · 🧪 PoC

## Beschreibung

urllib3 is an HTTP client library for Python. From 2.6.2 until 2.8.0, HTTPResponse.stream and HTTPResponse.read_chunked can enter an infinite loop because the Deflate decoder retains trailing bytes as unconsumed input after reaching end-of-stream and repeatedly decodes them without progress. The issue occurs when an untrusted server sends a chunked Deflate response whose decoded body exceeds a positive finite chunk size and whose encoded body has trailing bytes, specifically a response with Transfer-Encoding: chunked and Content-Encoding: deflate, content decoding enabled, and the positive finite amt=N streaming chunk size. The attack mechanism is that a malicious server returns a compressed chunked response with trailing bytes after the Deflate stream. The impact is excessive CPU usage and a request that does not complete, and network read timeouts do not interrupt the loop because no further socket read occurs. This issue is fixed in version 2.8.0.

## CNA-Record (Kanon, cvelistV5)

- CNA: **GitHub_M**
- State: PUBLISHED
- Stand: 2026-09-29 15:42:34
- CNA-CVSS: **6.9** (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`)

## CISA-Anreicherung (vulnrichment/ADP)

- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **none**
  - Automatable: **yes**
  - Technical Impact: **partial**

## CVSS-Vektor

```
CVSS:4.0/AV:N/AC:L/AT:N/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 |

## Schwachstellen-Klasse

- **CWE-835** — Loop with Unreachable Exit Condition ('Infinite Loop')
  The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.

## Patch verfügbar (OSV)

- b1d30ab61fe0db8f11092805e8c5ac43e091064a (Commit)
- ea2ad7b21a80da3632f80016526a18864586077f (Commit)

## Referenzen

- <https://github.com/urllib3/urllib3/security/advisories/GHSA-gh4c-6fx4-qh6g>
- <https://github.com/urllib3/urllib3/commit/ea2ad7b21a80da3632f80016526a18864586077f>
- <https://github.com/urllib3/urllib3/releases/tag/2.8.0>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-97688>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/sicherheitsluecken/cve-2026-97688/) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_