CVE-2025-66418

urllib3 is a user-friendly HTTP client library for Python. Starting in version 1.24 and prior to 2.6.0, the number of links in the decompression chain was unbounded allowing a malicious server to insert a virtually unlimited number of compression steps leading to high CPU usage and massive memory allocation for the decompressed data. This vulnerability is fixed in 2.6.0.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/urllib3/urllib3/commit/24d7b67eac89f94e11003424bcf0d8f7b72222a8	Patch
https://github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53	Vendor Advisory

Configurations

Configuration 1 (hide)

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

History

10 Dec 2025, 16:08

Type	Values Removed	Values Added
CVSS	v2 : ~~unknown~~ v3 : ~~unknown~~	v2 : unknown v3 : 7.5
CPE		cpe:2.3:a:python:urllib3::::::::
References	~~() https://github.com/urllib3/urllib3/commit/24d7b67eac89f94e11003424bcf0d8f7b72222a8 -~~	() https://github.com/urllib3/urllib3/commit/24d7b67eac89f94e11003424bcf0d8f7b72222a8 - Patch
References	~~() https://github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53 -~~	() https://github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53 - Vendor Advisory
First Time		Python Python urllib3

05 Dec 2025, 16:15

Type	Values Removed	Values Added
New CVE

Information

Published : 2025-12-05 16:15

Updated : 2025-12-10 16:08

NVD link : CVE-2025-66418

Mitre link : CVE-2025-66418

CVE.ORG link : CVE-2025-66418

JSON object : View

Products Affected

python

urllib3

CWE

CWE-770

Allocation of Resources Without Limits or Throttling

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