🛡️ CVE-2021-46823 — python-ldap

⚪ Unknown ✅ No Known Exploit CWE-1333 OSV
N/A
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

ReDoS in LDAP schema parser

https://github.com/python-ldap/python-ldap/issues/424

Impact

The LDAP schema parser of python-ldap 3.3.1 and earlier are vulnerable to a regular expression denial-of-service attack. The issue affects clients that use `ldap.schema` package to parse LDAP schema definitions from an untrusted source.

Patches

The upcoming release of python-ldap 3.4.0 will contain a workaround to prevent ReDoS attacks. The schema parser refuses schema definitions with an excessive amount of backslashes.

Workarounds

As a workaround, users can check input for excessive amount of backslashes in schemas. More than a dozen backslashes per line are atypical.

References

[CWE-1333](https://cwe.mitre.org/data/definitions/1333.html)

For more information

If you have any questions or comments about this advisory:

  • Open an issue in [python-ldap](https://github.com/python-ldap/python-ldap) tracker

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

Weakness class

CVE-2021-46823 is classified as CWE-1333: Inefficient Regular Expression Complexity. A regular expression backtracks catastrophically on crafted input, consuming CPU out of proportion to input size.

Affected software

CVE-2021-46823 is recorded against 1 package.

  • python-ldap (fixed in 3.4.0)

Timeline and source

Published on 19 June 2022 and last revised on 8 July 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

github.com (Web)
nvd.nist.gov (Advisory)
exchange.xforce.ibmcloud.com (Web)
github.com (Package)

CVE-2021-46823 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Unknown
CVSS Score N/A
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CWE CWE-1333
Public Exploit ✅ No
Source OSV
Published 2022-06-19
Updated 2026-08-12
Modified 2026-07-08
Fix URL N/A

Affected Packages

Software From version Fixed in
python-ldap — 3.4.0

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