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CriticalPython

CVE-2021-29921

In Python before 3,9,5, the ipaddress library mishandles leading zero characters in the octets of an IP address string. This (in some situations) allows attackers to bypass access control that is based on IP addresses.

CVSS Base Score
9.8

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploit Probability
94%EPSS PERCENTILE0100

More exploitable than 94% of all CVEs · Top 6%

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Details
Published
2021-05-06
Last modified
2026-10-08
Affected
Python
References
NVD Detail OSV.dev GitHub Advisories

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Data from the National Vulnerability Database (NVD), CISA KEV, and FIRST.org EPSS. This product uses the NVD API but is not endorsed or certified by the NVD. EPSS is a probability estimate, not a guarantee of exploitation.