CVE-2025-66418
python-urllib3 - security update
EPSS 0.63%
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.
How to fix CVE-2025-66418
To remediate CVE-2025-66418, upgrade the affected package to a fixed version below.
- PyPI/urllib3—upgrade to 2.6.0 or later
- —upgrade to 2.6.0 or later
Is CVE-2025-66418 being exploited?
Low — EPSS is 0.6%, meaning exploitation activity has not been observed at scale.
Affected packages (2)
- >= 1.24, < 2.6.0
- >= 1.24, < 2.6.0
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | 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 |