What’s Vulnerable › Vulnerabilities

CVE-2021-29921

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 6.9% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-05-06 · updated 2026-10-08

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.

Affected products

• Oracle Communications Cloud Native Core Automated Test Suite: 1.8.0
• Oracle Communications Cloud Native Core Binding Support Function: 1.11.0
• Oracle Communications Cloud Native Core Network Slice Selection Function: 1.8.0
• Oracle Corporation GraalVM Enterprise Edition: 20.3.2, 21.1.0
• Oracle Corporation Oracle ZFS Storage Appliance Kit: 8.8
• Python: from 3.8.0 before 3.8.12; from 3.9.0 before 3.9.5 — fixed in 3.8.12, 3.9.5

How to fix

Upgrade to a fixed version: Python 3.8.12, 3.9.5. Check the vendor advisory for mitigations.

References

• https://bugs.python.org/issue36384
• https://docs.python.org/3/library/ipaddress.html
• https://github.com/python/cpython/blob/63298930fb531ba2bb4f23bc3b915dbf1e17e9e1/Misc/NEWS.d/3.8.0a4.rst
• https://github.com/python/cpython/pull/12577
• https://github.com/python/cpython/pull/25099
• https://github.com/sickcodes
• https://github.com/sickcodes/security/blob/master/advisories/SICK-2021-014.md
• https://python-security.readthedocs.io/vuln/ipaddress-ipv4-leading-zeros.html
• https://security.gentoo.org/glsa/202305-02
• https://security.netapp.com/advisory/ntap-20210622-0003/
• https://sick.codes/sick-2021-014
• https://www.oracle.com//security-alerts/cpujul2021.html

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