CVE-2025-66418NVD

Vulnerability Summary

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.

Severity Level

HIGH(8.9)

Published Date

Dec 5, 2025

Last Modified

Dec 5, 2025

Exploitation Status

No confirmed exploitation yet

EPSS Score (30-Day)

Data Pending

Root Weakness (CWE)

CWE-770: Unknown/Unlisted Weakness ↗

Refer to the official MITRE database for detailed architectural specifications regarding this weakness.

CVSS v4.0 Base Metrics — Score 8.9 (HIGH)

Attack VectorNetwork

Attack ComplexityLow

Attack RequirementsPresent

Privileges RequiredNone

User InteractionNone

Confidentiality (Vulnerable System)None

Integrity (Vulnerable System)None

Availability (Vulnerable System)High

Confidentiality (Subsequent System)None

Integrity (Subsequent System)None

Availability (Subsequent System)High

Affected & Patched Versions

Affected Versions

Not provided by NVD for this CVE.

Patched Versions

Not provided by NVD for this CVE.

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