CVE-2025-66418
urllib3 allows an unbounded number of links in the decompression chain
- State
- Published
- Severity
- 8.9 High
- Published
- Dec 5, 2025
- Updated
- Dec 5, 2025
- Reserved
- Nov 28, 2025
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.9 High | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H | GitHub_M |
Weaknesses
- CWE-770 Allocation of Resources Without Limits or Throttling
Affected Products
| Product | Versions |
|---|---|
urllib3urllib3 |
|
References
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