CVE-2025-66418urllib3 is a user-friendly HTTP client library for Python.
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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
- 7.5 HIGH (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-770
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Analyzed
- Record last updated
- Sep 25, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
python urllib3 python:urllib3 | from 1.24 before 2.6.0 | NVD |
References
- https://github.com/urllib3/urllib3/commit/24d7b67eac89f94e11003424bcf0d8f7b72222a8patch
- https://github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53vendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.