Vulnerability Note VU#935800

Multiple versions of OpenLDAP are vulnerable to denial-of-service attacks

Original Release date: 16 Jul 2001 | Last revised: 12 Dec 2002


Multiple versions of OpenLDAP contain vulnerabilities that may allow denial-of-service attacks. These vulnerabilities were revealed using the PROTOS LDAPv3 test suite and are documented in CERT Advisory CA-2001-18. If your site uses this product, the CERT/CC encourages you to follow the advice provided below.


There are multiple vulnerabilities in the OpenLDAP implementations of the LDAP protocol. These vulnerabilities exist in the code that translates network datagrams into application-specific information.

In the encoding section of the test suite, this product failed the group that tests the handling of invalid BER length of length fields.

In the application section of the test suite, this product passed all 6685 test cases.


These vulnerabilities allow a remote attacker to crash affected OpenLDAP servers, resulting in a denial-of-service condition.


Apply a patch from your vendor

Please consult the Systems Affected section for vendor-specific information on addressing this vulnerability.

Block access to directory services at network perimeter

As a temporary measure, it is possible to limit the scope of these vulnerabilities by blocking access to directory services at the network perimeter. Please note that this workaround does not protect vulnerable products from internal attacks.

            ldap    389/tcp     # Lightweight Directory Access Protocol
            ldap    389/udp     # Lightweight Directory Access Protocol
            ldaps   636/tcp     # ldap protocol over TLS/SSL (was sldap)
            ldaps   636/udp     # ldap protocol over TLS/SSL (was sldap)

Systems Affected (Learn More)

VendorStatusDate NotifiedDate Updated
ConectivaAffected-01 Nov 2001
DebianAffected09 Aug 200112 Dec 2002
MandrakeSoftAffected13 Aug 200112 Dec 2002
OpenLDAPAffected03 May 200116 Jul 2001
Red Hat Inc.Affected-01 Nov 2001
If you are a vendor and your product is affected, let us know.

CVSS Metrics (Learn More)

Group Score Vector
Base N/A N/A
Temporal N/A N/A
Environmental N/A N/A



The CERT Coordination Center thanks the Oulu University Secure Programming Group for reporting these vulnerabilities to us, for their detailed technical analyses, and for their assistance in preparing this document. We would also like to thank the OpenLDAP Core Team for their assistance in preparing this document.

This document was written by Jeffrey P. Lanza.

Other Information

  • CVE IDs: CVE-2001-0977
  • CERT Advisory: CA-2001-18
  • Date Public: 16 Jul 2001
  • Date First Published: 16 Jul 2001
  • Date Last Updated: 12 Dec 2002
  • Severity Metric: 1.77
  • Document Revision: 53


If you have feedback, comments, or additional information about this vulnerability, please send us email.