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CVE-2025-66418

urllib3 allows an unbounded number of links in the decompression chain

Published: Dec 5, 2025Updated: Dec 10, 2025 Sources: CVE List NVD GHSA BDUCWE-770
7.5HIGH
NVD MITRE
EPSS Score
0.7%
Top 50.6%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
OpenVAS

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:NI:NA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:HAvailability
High
Open in CVSS calculator →

Weaknesses

CWE-770

Affected Products

Red Hat Inc.
commercial·USaka red hat
Red Hat Enterprise LinuxOn-premOS
Operating Systems / linux-distro
OpenShift Container PlatformOn-prem
Operating Systems / linux-distro
Ansible Automation PlatformOn-prem
Operating Systems / linux-distro
Red Hat Openshift Data FoundationOn-prem
Operating Systems / linux-distro
Red Hat SatelliteOn-prem
Operating Systems / linux-distro
Migration Toolkit for VirtualizationOn-prem
Operating Systems / linux-distro
OpenShift ServerlessOn-prem
Operating Systems / linux-distro
OpenShift Dev SpacesOn-prem
Operating Systems / linux-distro
Fedora Project
oss-project·USaka fedora
FedoraOn-premOS
Operating Systems / linux-distro
Fedora EPELOn-prem
Operating Systems / linux-distro
python
oss-project·US
urllib3
OSS Libraries
urllib3
oss-project
urllib3Library
OSS Libraries / pypi
Canonical Ltd.
commercial·GBaka canonical
UbuntuOn-premOS
Operating Systems / linux-distro
Сообщество свободного программного обеспечения
oss-projectaka fsf
Debian GNU/LinuxOn-premOS
Operating Systems / linux-distro
and 37 more affected products View all →

Exploitability

Official Patch Available
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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

1 technique
Impact
View detailed technique mapping

References

https://github.com/urllib3/urllib3/commit/24d7b67eac89f94e11003424bcf0d8f7b72222a8
github.com
https://github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53
github.com
https://github.com/urllib3/urllib3/commit/24d7b67eac89f94e11003424bcf0d8f7b72222a8
github.com
and 13 more references View all →

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