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

25 Sep 2026, 23:10

Type	Values Removed	Values Added
Summary		(es) urllib3 es una biblioteca cliente HTTP fácil de usar para Python. A partir de la versión 1.24 y en versiones anteriores a la 2.6.0, el número de enlaces en la cadena de descompresión era ilimitado, lo que permitía a un servidor malicioso insertar un número prácticamente ilimitado de pasos de compresión, lo que provocaba un alto uso de CPU y una asignación masiva de memoria para los datos descomprimidos. Esta vulnerabilidad se corrigió en la versión 2.6.0.

Information

Published : 2025-12-05 16:15

Updated : 2026-09-25 23:10

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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