Headline
CVE-2021-46823
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.
#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
For more information
If you have any questions or comments about this advisory:
- Open an issue in python-ldap tracker
Related news
Ubuntu Security Notice 5508-1 - It was discovered that Python LDAP incorrectly handled certain regular expressions. An remote attacker could possibly use this issue to cause a denial of service.
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.