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Critical 9.8Published May 6, 2021
CVE-2021-29921In Python before 3,9,5, the ipaddress library mishandles leading zero characters in the octets of an IP address string.
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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
- 9.8 CRITICAL (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- mitre
- NVD analysis
- Modified
- Record last updated
- Oct 8, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
python python python:python | from 3.8.0 before 3.8.12; from 3.9.0 before 3.9.5 | NVD |
oracle communications_cloud_native_core_automated_test_suite oracle:communications_cloud_native_core_automated_test_suite | 1.8.0 | NVD |
oracle communications_cloud_native_core_binding_support_function oracle:communications_cloud_native_core_binding_support_function | 1.11.0 | NVD |
oracle communications_cloud_native_core_network_slice_selection_function oracle:communications_cloud_native_core_network_slice_selection_function | 1.8.0 | NVD |
oracle graalvm oracle:graalvm | 20.3.2; 21.1.0 | NVD |
oracle zfs_storage_appliance_kit oracle:zfs_storage_appliance_kit | 8.8 | NVD |
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/202305-02vendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.