CVE-2025-66418
HIGH7.5EPSS 0.02%python-urllib3 - security update
Published: 12/5/2025Modified: 1/17/2026
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.
Affected packages (4)
- Alpine/py3-urllib3from 0, < 2.6.3-r0
- Debian/python-urllib3from 0, < 1.26.5-1~exp1+deb11u2
- Debian/python-urllib3from 0, < 1.26.12-1+deb12u2
- PyPI/urllib3>= 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 |
| osv | CVSS 3.1 | HIGH7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
References (6)
- ADVISORYhttps://nvd.nist.gov/vuln/detail/CVE-2025-66418
- ADVISORYhttps://security.alpinelinux.org/vuln/CVE-2025-66418
- ADVISORYhttps://security-tracker.debian.org/tracker/CVE-2025-66418
- PATCHhttps://github.com/urllib3/urllib3
- WEBhttps://github.com/urllib3/urllib3/commit/24d7b67eac89f94e11003424bcf0d8f7b72222a8
- WEBhttps://github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53