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Python LdapApplication

CVE-2021-46823

MEDIUM · 6.5 CVSS v3.1 Published 2022-06-18
Fix available
A fix is available. Upgrade to 3.4.0 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

python-ldap versions before 3.4.0 contain a ReDoS vulnerability in the ldap.schema module's schema parser. When processing untrusted schema definitions containing crafted regex input, the regular expression engine can be forced into excessive backtracking, causing the application to become unresponsive. An attacker needs authenticated access to submit malicious schema data to trigger this condition.

MitigationUpgrade python-ldap to version 3.4.0 or later. If immediate upgrade is not feasible, restrict or validate schema input from untrusted sources and consider implementing request rate limiting to mitigate DoS attempts.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Python LdapApplication
Affected:< 3.4.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed python-ldap version
    Run 'pip show python-ldap' or check your requirements.txt/poetry.lock file for the python-ldap version
    Affected if The version is lower than 3.4.0 (e.g., 3.3.x, 3.2.x, etc.)
  2. Verify ldap.schema module usage
    Search your codebase for imports or usage of 'ldap.schema' or 'from ldap import schema' statements
    Affected if The ldap.schema module is imported or used in your application code
  3. Check for schema processing from LDAP sources
    Review code that calls schema parsing functions such as ldap.schema.SubSchema or schema parsing methods that process LDAP schema definitions
    Affected if Your application retrieves or parses schema data from external LDAP directories
  4. Inspect runtime dependencies
    Run 'pip list | grep -i ldap' or examine your application's dependency tree to confirm python-ldap is present
    Affected if python-ldap package is listed in your environment dependencies

You are affected if python-ldap version is below 3.4.0 AND your application uses the ldap.schema module to process schema data from LDAP sources.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 3.4.0 or later
Fixed in 3.4.0
Interim mitigation

Upgrade python-ldap to version 3.4.0 or later. If immediate upgrade is not feasible, restrict or validate schema input from untrusted sources and consider implementing request rate limiting to mitigate DoS attempts.

Recommended fix High confidence

python-ldap >= 3.4.0

  1. Verify the current installed version of python-ldap by running: pip show python-ldap or pip freeze | grep python-ldap
  2. Upgrade python-ldap to version 3.4.0 or later using: pip install --upgrade python-ldap
  3. Verify the upgrade was successful by running: pip show python-ldap to confirm the installed version is >= 3.4.0
  4. If your application uses ldap.schema with untrusted input, ensure schema definitions are validated or from trusted sources only

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Python Ldap Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,664.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-46823 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data