Is there a public exploit for CVE-2025-66418?

No public exploit for CVE-2025-66418 was found in Exploit-DB, Metasploit, Nuclei templates or public proof-of-concept repositories. That is an absence of evidence rather than proof that none exists.

How severe is CVE-2025-66418?

CVE-2025-66418 scores CVSS 8.9 (v4.0), rated high. EPSS puts the chance of exploitation in the next 30 days at 0.73%.

What does CVE-2025-66418 affect?

CVE-2025-66418 affects urllib3 urllib3.

8.9 High

urllib3 is a user-friendly HTTP client library for Python.

CVE-2025-66418

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.

Assessment

CVSS: 8.9 (v4.0)
Severity: High
EPSS: 0.73% chance of exploitation in the next 30 days
Known exploited: Not listed in CISA KEV
Exploit availability: Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
Published: 5 December 2025
Last updated: 25 September 2026
Affected: urllib3 · urllib3
Weakness: CWE-770
Assigner: security-advisories@github.com

CVSS vectorCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

At the source

References

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