CVE-2025-66418
December 05, 2025
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.
Affected Packages
urllib3 (CONDA):
Affected version(s) >=1.24 <2.6.0Fix Suggestion:
Update to version 2.6.0https://github.com/urllib3/urllib3.git (GITHUB):
Affected version(s) >=1.24 <2.6.0Fix Suggestion:
Update to version 2.6.0urllib3 (PYTHON):
Affected version(s) >=1.24 <2.6.0Fix Suggestion:
Update to version 2.6.0Related Resources (4)
Do you need more information?
Contact UsCVSS v4
Base Score:
8.9
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
PRESENT
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
NONE
Vulnerable System Availability
HIGH
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
HIGH
CVSS v3
Base Score:
8.6
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Weakness Type (CWE)
Allocation of Resources Without Limits or Throttling
EPSS
Base Score:
0.03
