CVE-2021-29921Published
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.
Exact source revision recorded 23 Oct 2026 15:48:27 UTC. It does not establish the source's current position. Latest evidence.
Explicit identifiers and source references
These records connect through source-stated identifiers. Shared identifiers or dates alone do not establish shared exposure, root cause or applicability.
CVE-2021-29921 · Microsoft / collected KEV context
cve-program · CVE-2021-29921
- https://github.com/sickcodes
- https://docs.python.org/3/library/ipaddress.html
- https://github.com/python/cpython/blob/63298930fb531ba2bb4f23bc3b915dbf1e17e9e1/Misc/NEWS.d/3.8.0a4.rst
- https://sick.codes/sick-2021-014
- https://www.oracle.com//security-alerts/cpujul2021.html
- https://github.com/sickcodes/security/blob/master/advisories/SICK-2021-014.md
- https://python-security.readthedocs.io/vuln/ipaddress-ipv4-leading-zeros.html
- https://bugs.python.org/issue36384
- https://github.com/python/cpython/pull/12577
- https://github.com/python/cpython/pull/25099
- https://security.netapp.com/advisory/ntap-20210622-0003/
- https://www.oracle.com/security-alerts/cpuoct2021.html
- https://www.oracle.com/security-alerts/cpujan2022.html
- https://www.oracle.com/security-alerts/cpuapr2022.html
- https://www.oracle.com/security-alerts/cpujul2022.html
- https://security.gentoo.org/glsa/202305-02
Current operational correlations are not mixed into this historical source record. Open latest evidence to discover current connections.