CVE-2021-46823: Python ldap Denial of Service Vulnerability

MODERATE
Advisory Identifier: GHSA-qfr5-wjpw-q4c4
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CVSS 6.5
CWE-1333
Published
Advisory Summary

CVE-2021-46823 is a MODERATE (CVSS 6.5) denial of service vulnerability (CWE-1333: Inefficient Regular Expression Complexity) affecting Python ldap libraries in the PyPI ecosystem. The issue involves denial of service in python-ldap. Remediation is available by upgrading affected packages to version 3.4.0.

CVE-2021-46823 at a Glance

CVE Identifier CVE-2021-46823
GHSA Identifier GHSA-qfr5-wjpw-q4c4
Severity MODERATE
CVSS v3.1 Base Score 6.5
CWE Classification CWE-1333: Inefficient Regular Expression Complexity
Affected Product Python ldap
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 6.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2021-46823

To remediate this vulnerability, upgrade all affected Python ldap dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

python-ldap fixed: 3.4.0 
pip install python-ldap>=3.4.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show python-ldap

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2021-46823, inspect your installed packages using pip:

pip show python-ldap

Analyze the terminal output to locate any version of Python ldap in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.4.0), your application is affected.

Note: The pip show python-ldap command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-1333: Inefficient Regular Expression Complexity, where the product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential. In Python ldap, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

python-ldap before 3.4.0 is vulnerable to a denial of service when ldap.schema is used for untrusted schema definitions, because of a regular expression denial of service (ReDoS) flaw in the LDAP schema parser. By sending crafted regex input, a remote authenticated attacker could exploit this vulnerability to cause a denial of service condition.

CVE-2021-46823 Affected Python ldap Versions

1 component(s)
Fixed Versions:
3.4.0
Product / Package Ecosystem Affected Versions Fixed Version
python-ldap
pypi/python-ldap
PyPI
< 3.4.0
3.4.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/python-ldap/python-ldap/security/advisories/GHSA-r8wq-qrxc-hmcm
NVD — CVE-2021-46823 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-46823
exchange.xforce.ibmcloud.com/vulnerabilities/221... WEB
https://exchange.xforce.ibmcloud.com/vulnerabilities/221507
Python ldap Source Repository REPOSITORY
https://github.com/python-ldap/python-ldap

Frequently Asked Questions

What is CVE-2021-46823?
CVE-2021-46823 is a security vulnerability in Python ldap involving Denial of Service in python-ldap under CWE-1333: Inefficient Regular Expression Complexity.
Which Python ldap versions are affected?
Affected versions include releases prior to 3.4.0 across affected packages: python-ldap.
What version fixes CVE-2021-46823?
Upgrading to 3.4.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is python-ldap affected?
Yes, python-ldap is affected in releases prior to 3.4.0. Upgrade your dependency to 3.4.0 or later.
What is the CVSS score of CVE-2021-46823?
CVE-2021-46823 has a CVSS v3.1 base score of 6.5 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2021-46823?
CVE-2021-46823 is classified under CWE-1333: Inefficient Regular Expression Complexity (The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.).
How can I check PyPI dependencies for CVE-2021-46823?
Run the dependency tree command: 'pip show python-ldap'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-qfr5-wjpw-q4c4",
  "modified" : "2022-06-29T21:52:17Z",
  "published" : "2022-06-19T00:00:21Z",
  "aliases" : [ "CVE-2021-46823" ],
  "summary" : "Denial of Service in python-ldap",
  "details" : "python-ldap before 3.4.0 is vulnerable to a denial of service when ldap.schema is used for untrusted schema definitions, because of a regular expression denial of service (ReDoS) flaw in the LDAP schema parser. By sending crafted regex input, a remote authenticated attacker could exploit this vulnerability to cause a denial of service condition.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "python-ldap"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.4.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/python-ldap/python-ldap/security/advisories/GHSA-r8wq-qrxc-hmcm"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-46823"
  }, {
    "type" : "WEB",
    "url" : "https://exchange.xforce.ibmcloud.com/vulnerabilities/221507"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/python-ldap/python-ldap"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1333" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-06-20T22:36:32Z",
    "nvd_published_at" : "2022-06-18T16:15:00Z"
  }
}