CVE-2021-29921

CRITICALImmediate

Published:May 6, 2021(5 years ago)

Modified:Nov 3, 2025

Remote ExploitNo Auth RequiredNo InteractionLow Complexity

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.

Attack Characteristics

Network AccessLow ComplexityNo Auth NeededNo User Interaction

🤖

AI analysis not yet available

Plain-English explanation, risk summary, and remediation steps will appear here once AI analysis is complete.

No Fix Known

No patch has been released yet. Apply workarounds or mitigations where available.

Affected Software

Vendor	Product	Versions	Fixed In
python	python	3.8.0 - 3.8.12	-
python	python	3.9.0 - 3.9.5	-
oracle	communications_cloud_native_core_automated_test_suite

Timeline

Published
CVE disclosed publicly
May 6, 20215 years ago
Last Modified
Most recent update
Nov 3, 20256 months ago
Indexed to CVEInsight
Added to this platform
Mar 29, 20261 month ago

References

https://bugs.python.org/issue36384Issue Tracking
https://docs.python.org/3/library/ipaddress.htmlVendor Advisory
https://github.com/python/cpython/blob/63298930fb531ba2bb4f23bc3b915db...Third Party Advisory

CVSS Score

v3.1

9.8/ 10.0

CRITICAL

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

At a Glance

Affected Products

References

python / python

https://github.com/python/cpython/pull/12577Patch

https://github.com/python/cpython/pull/25099Patch

https://github.com/sickcodesThird Party Advisory

https://github.com/sickcodes/security/blob/master/advisories/SICK-2021...Exploit

https://python-security.readthedocs.io/vuln/ipaddress-ipv4-leading-zer...Vendor Advisory

https://security.gentoo.org/glsa/202305-02

https://security.netapp.com/advisory/ntap-20210622-0003/Third Party Advisory

https://sick.codes/sick-2021-014Exploit

https://www.oracle.com//security-alerts/cpujul2021.htmlPatch

https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch

https://www.oracle.com/security-alerts/cpujan2022.htmlPatch

https://www.oracle.com/security-alerts/cpujul2022.html

https://www.oracle.com/security-alerts/cpuoct2021.htmlPatch

https://bugs.python.org/issue36384Issue Tracking

https://docs.python.org/3/library/ipaddress.htmlVendor Advisory

https://github.com/python/cpython/blob/63298930fb531ba2bb4f23bc3b915db...Third Party Advisory

https://github.com/python/cpython/pull/12577Patch

https://github.com/python/cpython/pull/25099Patch

https://github.com/sickcodesThird Party Advisory

https://github.com/sickcodes/security/blob/master/advisories/SICK-2021...Exploit

https://lists.debian.org/debian-lts-announce/2024/12/msg00000.html

https://python-security.readthedocs.io/vuln/ipaddress-ipv4-leading-zer...Vendor Advisory

https://security.gentoo.org/glsa/202305-02

https://security.netapp.com/advisory/ntap-20210622-0003/Third Party Advisory

https://sick.codes/sick-2021-014Exploit

https://www.oracle.com//security-alerts/cpujul2021.htmlPatch

https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch

https://www.oracle.com/security-alerts/cpujan2022.htmlPatch

https://www.oracle.com/security-alerts/cpujul2022.html

https://www.oracle.com/security-alerts/cpuoct2021.htmlPatch

CVSS v3 Vector

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

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

Impact

ScopeUnchanged

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

Impact Analysis

ConfidentialityHigh

NoneLowHigh

IntegrityHigh

NoneLowHigh

AvailabilityHigh

NoneLowHigh

CVE-2021-29921

✦ Vulnerability Description

Attack Characteristics

Affected Software

Timeline

References

CVSS Score

At a Glance

Official Sources

CVSS v3 Vector

Impact Analysis

Vulnerability Description