01 Record

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

UnratedPUBLISHEDCNA: mitre

CNA base scoreUnratedNo CNA CVSS vector

View raw JSON

02 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

03 Exploitation and scoring

Exploitation

Assessed, none found. CISA's assessment recorded neither public exploit code nor evidence of exploitation when it was made.

SSVC decision

ExploitationnoneCISA recorded no public exploit code and no evidence of exploitation.
AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
Technical ImpacttotalSuccessful exploitation gives total control of the vulnerable component.

CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.

EPSS probability

6.88% probability of exploitation activity in the next 30 days.

EPSS percentile

Equal to or higher than the score of 93.9% of scored records. A rank, not a probability.

NVD base score

9.8 (CVSS v3.x), scored by the NVD independently of the CNA.

NVD CVSS vector

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

NVD analysis status

Modified. NVD last modified this record on 2026-10-08.

Red Hat severity

Moderate. Red Hat's rating for its own products, not a CVSS rating.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published: 2021-05-06 00:00Z5 YR AGO
Last updated: 2026-10-08 21:13Z20 DAYS AGO
Reserved: 2021-04-01
Assigning CNA: mitre
Record state: PUBLISHED
Severity: Not rated by the issuing CNA
CNA CVSS vector: Not published by the issuing CNA
Weaknesses: No CWE assigned
Data version: 5.2
Document digest: 29b2db1bd1cf324e53a9b517f655b4d814e667ba0dab4131e97c1add4e634636

05 Affected products

VendorProductVersionsPlatforms

oraclecommunications_cloud_native_core_automated_test_suiteNot specified—

oraclecommunications_cloud_native_core_binding_support_functionNot specified—

oraclecommunications_cloud_native_core_network_slice_selection_functionNot specified—

oraclegraalvmNot specified—

oraclezfs_storage_appliance_kitNot specified—

pythonpythonNot specified—

redhatenterprise_linuxNot specified—

redhatrhel_software_collectionsNot specified—

06 References

github.comhttps://github.com/sickcodes
docs.python.orghttps://docs.python.org/3/library/ipaddress.html
github.comhttps://github.com/python/cpython/blob/63298930fb531ba2bb4f23bc3b915dbf1e17e9e1/Misc/NEWS.d/3.8.0a4.rst
sick.codeshttps://sick.codes/sick-2021-014
www.oracle.comhttps://www.oracle.com//security-alerts/cpujul2021.html
github.comhttps://github.com/sickcodes/security/blob/master/advisories/SICK-2021-014.md
python-security.readthedocs.iohttps://python-security.readthedocs.io/vuln/ipaddress-ipv4-leading-zeros.html
bugs.python.orghttps://bugs.python.org/issue36384
github.comhttps://github.com/python/cpython/pull/12577
github.comhttps://github.com/python/cpython/pull/25099
security.netapp.comhttps://security.netapp.com/advisory/ntap-20210622-0003/
www.oracle.comhttps://www.oracle.com/security-alerts/cpuoct2021.html
www.oracle.comhttps://www.oracle.com/security-alerts/cpujan2022.html
www.oracle.comhttps://www.oracle.com/security-alerts/cpuapr2022.html
www.oracle.comhttps://www.oracle.com/security-alerts/cpujul2022.html
security.gentoo.orgGLSA-202305-02https://security.gentoo.org/glsa/202305-02vendor-advisory
lists.debian.orghttps://lists.debian.org/debian-lts-announce/2024/12/msg00000.html

07 Fixed in

AlmaLinux 8

python38-Cython
Fixed in 0.29.14-4.module_el8.6.0+2778+cd494b30
python38-PyMySQL
Fixed in 0.10.1-1.module_el8.6.0+2778+cd494b30
python38-asn1crypto
Fixed in 1.2.0-3.module_el8.6.0+2778+cd494b30
python38-atomicwrites
Fixed in 1.3.0-8.module_el8.6.0+2778+cd494b30
python38-attrs
Fixed in 19.3.0-3.module_el8.6.0+2778+cd494b30
python38-babel
Fixed in 2.7.0-11.module_el8.6.0+2778+cd494b30
python38-cffi
Fixed in 1.13.2-3.module_el8.6.0+2778+cd494b30
python38-chardet
Fixed in 3.0.4-19.module_el8.6.0+2778+cd494b30
python38-cryptography
Fixed in 2.8-3.module_el8.6.0+2778+cd494b30
python38-idna
Fixed in 2.8-6.module_el8.6.0+2778+cd494b30
python38-jinja2
Fixed in 2.10.3-5.module_el8.6.0+2778+cd494b30
python38-markupsafe
Fixed in 1.1.1-6.module_el8.6.0+2778+cd494b30
python38-mod_wsgi
Fixed in 4.6.8-3.module_el8.6.0+2778+cd494b30
python38-more-itertools
Fixed in 7.2.0-5.module_el8.6.0+2778+cd494b30
python38-numpy
Fixed in 1.17.3-6.module_el8.6.0+2778+cd494b30
python38-numpy-doc
Fixed in 1.17.3-6.module_el8.6.0+2778+cd494b30
python38-numpy-f2py
Fixed in 1.17.3-6.module_el8.6.0+2778+cd494b30
python38-packaging
Fixed in 19.2-3.module_el8.6.0+2778+cd494b30
python38-pluggy
Fixed in 0.13.0-3.module_el8.6.0+2778+cd494b30
python38-ply
Fixed in 3.11-10.module_el8.6.0+2778+cd494b30
python38-psutil
Fixed in 5.6.4-4.module_el8.6.0+2778+cd494b30
python38-psycopg2
Fixed in 2.8.4-4.module_el8.6.0+2778+cd494b30
python38-psycopg2-doc
Fixed in 2.8.4-4.module_el8.6.0+2778+cd494b30
python38-psycopg2-tests
Fixed in 2.8.4-4.module_el8.6.0+2778+cd494b30
python38-py
Fixed in 1.8.0-8.module_el8.6.0+2778+cd494b30
python38-pycparser
Fixed in 2.19-3.module_el8.6.0+2778+cd494b30
python38-pyparsing
Fixed in 2.4.5-3.module_el8.6.0+2778+cd494b30
python38-pysocks
Fixed in 1.7.1-4.module_el8.6.0+2778+cd494b30
python38-pytest
Fixed in 4.6.6-3.module_el8.6.0+2778+cd494b30
python38-pytz
Fixed in 2019.3-3.module_el8.6.0+2778+cd494b30
python38-pyyaml
Fixed in 5.4.1-1.module_el8.6.0+2778+cd494b30
python38-requests
Fixed in 2.22.0-9.module_el8.6.0+2778+cd494b30
python38-scipy
Fixed in 1.3.1-4.module_el8.6.0+2778+cd494b30
python38-setuptools
Fixed in 41.6.0-5.module_el8.6.0+2778+cd494b30
python38-setuptools-wheel
Fixed in 41.6.0-5.module_el8.6.0+2778+cd494b30
python38-six
Fixed in 1.12.0-10.module_el8.6.0+2778+cd494b30
python38-urllib3
Fixed in 1.25.7-5.module_el8.6.0+2778+cd494b30
python38-wcwidth
Fixed in 0.1.7-16.module_el8.6.0+2778+cd494b30
python38-wheel
Fixed in 0.33.6-6.module_el8.6.0+2778+cd494b30
python38-wheel-wheel
Fixed in 0.33.6-6.module_el8.6.0+2778+cd494b30

36 further packages in AlmaLinux 8 not shown (first 40 listed).

Arch Linux

python
Fixed in 3.9.5-1

Source: Arch Linux Security Tracker, the Arch Linux security team. Reformatted by exploit.cc.

CloudLinux 8

python38-Cython
Fixed in 0.29.14-4.module_el8.6.0+2778+cd494b30
python38-PyMySQL
Fixed in 0.10.1-1.module_el8.6.0+2778+cd494b30
python38-asn1crypto
Fixed in 1.2.0-3.module_el8.6.0+2778+cd494b30
python38-atomicwrites
Fixed in 1.3.0-8.module_el8.6.0+2778+cd494b30
python38-attrs
Fixed in 19.3.0-3.module_el8.6.0+2778+cd494b30
python38-babel
Fixed in 2.7.0-11.module_el8.6.0+2778+cd494b30
python38-cffi
Fixed in 1.13.2-3.module_el8.6.0+2778+cd494b30
python38-chardet
Fixed in 3.0.4-19.module_el8.6.0+2778+cd494b30
python38-cryptography
Fixed in 2.8-3.module_el8.6.0+2778+cd494b30
python38-idna
Fixed in 2.8-6.module_el8.6.0+2778+cd494b30
python38-jinja2
Fixed in 2.10.3-5.module_el8.6.0+2778+cd494b30
python38-markupsafe
Fixed in 1.1.1-6.module_el8.6.0+2778+cd494b30
python38-mod_wsgi
Fixed in 4.6.8-3.module_el8.6.0+2778+cd494b30
python38-more-itertools
Fixed in 7.2.0-5.module_el8.6.0+2778+cd494b30
python38-numpy
Fixed in 1.17.3-6.module_el8.6.0+2778+cd494b30
python38-numpy-doc
Fixed in 1.17.3-6.module_el8.6.0+2778+cd494b30
python38-numpy-f2py
Fixed in 1.17.3-6.module_el8.6.0+2778+cd494b30
python38-packaging
Fixed in 19.2-3.module_el8.6.0+2778+cd494b30
python38-pluggy
Fixed in 0.13.0-3.module_el8.6.0+2778+cd494b30
python38-ply
Fixed in 3.11-10.module_el8.6.0+2778+cd494b30
python38-psutil
Fixed in 5.6.4-4.module_el8.6.0+2778+cd494b30
python38-psycopg2
Fixed in 2.8.4-4.module_el8.6.0+2778+cd494b30
python38-psycopg2-doc
Fixed in 2.8.4-4.module_el8.6.0+2778+cd494b30
python38-psycopg2-tests
Fixed in 2.8.4-4.module_el8.6.0+2778+cd494b30
python38-py
Fixed in 1.8.0-8.module_el8.6.0+2778+cd494b30
python38-pycparser
Fixed in 2.19-3.module_el8.6.0+2778+cd494b30
python38-pyparsing
Fixed in 2.4.5-3.module_el8.6.0+2778+cd494b30
python38-pysocks
Fixed in 1.7.1-4.module_el8.6.0+2778+cd494b30
python38-pytest
Fixed in 4.6.6-3.module_el8.6.0+2778+cd494b30
python38-pytz
Fixed in 2019.3-3.module_el8.6.0+2778+cd494b30
python38-pyyaml
Fixed in 5.4.1-1.module_el8.6.0+2778+cd494b30
python38-requests
Fixed in 2.22.0-9.module_el8.6.0+2778+cd494b30
python38-scipy
Fixed in 1.3.1-4.module_el8.6.0+2778+cd494b30
python38-setuptools
Fixed in 41.6.0-5.module_el8.6.0+2778+cd494b30
python38-setuptools-wheel
Fixed in 41.6.0-5.module_el8.6.0+2778+cd494b30
python38-six
Fixed in 1.12.0-10.module_el8.6.0+2778+cd494b30
python38-urllib3
Fixed in 1.25.7-5.module_el8.6.0+2778+cd494b30
python38-wcwidth
Fixed in 0.1.7-16.module_el8.6.0+2778+cd494b30
python38-wheel
Fixed in 0.33.6-6.module_el8.6.0+2778+cd494b30
python38-wheel-wheel
Fixed in 0.33.6-6.module_el8.6.0+2778+cd494b30

36 further packages in CloudLinux 8 not shown (first 40 listed).

Derived from AlmaLinux 8. Partial coverage: only packages taken from AlmaLinux 8 are listed.

Debian 12

pypy3
Fixed in 7.3.8+dfsg-1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 13

pypy3
Fixed in 7.3.8+dfsg-1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 14

pypy3
Fixed in 7.3.8+dfsg-1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 20.04 LTS

python3.8
Fixed in 3.8.10-0ubuntu1~20.04.1
python3.9
Fixed in 3.9.5-3~20.04.1

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu Pro 18.04 LTS

python3.8
Fixed in 3.8.0-3ubuntu1~18.04.2+esm2
Available with Ubuntu Pro: https://ubuntu.com/pro

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

A release or ecosystem missing from this list has no record here. It may be unaffected or not covered by the source. Source notices and licences.