CVE-2026-97688

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.
Configurations

Configuration 1 (hide)

cpe:2.3:a:python:urllib3:*:*:*:*:*:*:*:*

History

13 Oct 2026, 20:21

Type Values Removed Values Added
References () https://github.com/urllib3/urllib3/commit/ea2ad7b21a80da3632f80016526a18864586077f - () https://github.com/urllib3/urllib3/commit/ea2ad7b21a80da3632f80016526a18864586077f - Patch
References () https://github.com/urllib3/urllib3/releases/tag/2.8.0 - () https://github.com/urllib3/urllib3/releases/tag/2.8.0 - Release Notes
References () https://github.com/urllib3/urllib3/security/advisories/GHSA-gh4c-6fx4-qh6g - () https://github.com/urllib3/urllib3/security/advisories/GHSA-gh4c-6fx4-qh6g - Mitigation, Vendor Advisory
CPE cpe:2.3:a:python:urllib3:*:*:*:*:*:*:*:*
First Time Python urllib3
Python
CVSS v2 : unknown
v3 : unknown
v2 : unknown
v3 : 5.3

29 Sep 2026, 16:17

Type Values Removed Values Added
New CVE

Information

Published : 2026-09-29 16:17

Updated : 2026-10-13 20:21


NVD link : CVE-2026-97688

Mitre link : CVE-2026-97688

CVE.ORG link : CVE-2026-97688


JSON object : View

Products Affected

python

  • urllib3
CWE
CWE-835

Loop with Unreachable Exit Condition ('Infinite Loop')