Back to Database
Status published
Critical
CVE-2021-29921
In Python before 3,9,5, the ipaddress library mishandles leading zero...
Vulnerability Description
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.
Impact Analysis
Refer to official advisory for detailed impact metrics.
Remediation
Ensure systems are updated to the latest vendor-supplied patch levels.
THREAT MONITOR
Am I Vulnerable?
Launch our assessment wizard to check if your infrastructure is exposed to • CVE-2021-29921
Credits & Attribution
No credits recorded in the NVD database.
References
- 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
More from python
View All →CVE-2022-48566
An issue was discovered in compare_digest in Lib/hmac.py in Python...
Medium
5.9
CVE-2022-48565
An XML External Entity (XXE) issue was discovered in Python...
Critical
9.8
CVE-2022-48564
read_ints in plistlib.py in Python through 3.9.1 is vulnerable to...
Medium
6.5
CVE-2022-48560
A use-after-free exists in Python through 3.9 via heappushpop in...
High
7.5
CVE-2022-45199
Pillow before 9.3.0 allows denial of service via SAMPLESPERPIXEL....
High
7.5
Affected Vendor
python
View all reports →Affected Software
python, communications cloud native core automated test suite, communications cloud native core binding support function, communications cloud native core network slice selection function, graalvm, zfs storage appliance kit
Vulnerable Versions:
3.8.0, 3.9.0, 1.8.0, 1.11.0, 20.3.2, 21.1.0, 8.8
Timeline
Official Publish:
May 6th, 2021
Last Modified:
November 3rd, 2025
Added to House:
July 21st, 2026
CVSS Vectors
V3:
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weaknesses (CWE)
No CWE data available
MITRE ATT&CK TTPs
No associated TTPs found for this vulnerability.