VDB-174596 · CVE-2021-29921 · Nessus 211991

Python up to 3.9.4 ipaddress Library input validation

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
8.4	$0-$5k	0.00

Summaryinfo

A vulnerability, which was classified as critical, was found in Python up to 3.9.4. This issue affects some unknown processing of the component ipaddress Library. Such manipulation leads to input validation. This vulnerability is documented as CVE-2021-29921. The attack can be executed remotely. There is not any exploit available. It is advisable to implement a patch to correct this issue.

Detailsinfo

A vulnerability was found in Python up to 3.9.4 (Programming Language Software) and classified as critical. Affected by this issue is some unknown functionality of the component ipaddress Library. The manipulation with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The weakness was released 05/06/2021. The advisory is shared for download at bugs.python.org. This vulnerability is handled as CVE-2021-29921. There are neither technical details nor an exploit publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 211991 (Debian dla-3980 : idle-python3.9 - security update), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 3.9.5 eliminates this vulnerability. Applying a patch is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be patching the affected component.

The vulnerability is also documented in the vulnerability database at Tenable (211991). Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

Programming Language Software

Name

Python

Version

License

open-source

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 8.5
VulDB Meta Temp Score: 8.4

VulDB Base Score: 7.3
VulDB Temp Score: 7.0
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 9.8
NVD Vector: 🔍

CVSSv2info

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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

NVD Base Score: 🔍

Exploitinginfo

Class: Input validation
CWE: CWE-20
CAPEC: 🔍
ATT&CK: 🔍

Physical: No
Local: No
Remote: Yes

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

0-Day	Unlock	Unlock	Unlock	Unlock
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Nessus ID: 211991
Nessus Name: Debian dla-3980 : idle-python3.9 - security update

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

0-Day Time: 🔍

Upgrade: Python 3.9.5
Patch: github.com

Timelineinfo

04/01/2021 🔍
05/06/2021 +35 days 🔍
05/06/2021 +0 days 🔍
11/04/2025 +1643 days 🔍

Sourcesinfo

Advisory: bugs.python.org
Status: Confirmed

CVE: CVE-2021-29921 (🔍)
GCVE (CVE): GCVE-0-2021-29921
GCVE (VulDB): GCVE-100-174596

Entryinfo

Created: 05/06/2021 18:05
Updated: 11/04/2025 04:09
Changes: 05/06/2021 18:05 (37), 05/09/2021 16:17 (5), 10/12/2021 11:12 (22), 10/12/2021 11:16 (2), 12/02/2024 17:07 (16), 11/04/2025 04:09 (2)
Complete: 🔍
Cache ID: 216::103