Finding and Fixing Vulnerabilities in Malformed Bind Request (LDAP Anonymous), a Medium Risk Vulnerability

With Notes on Remediation, Penetration Testing, Disclosures, Patching and Exploits

Vulnerabilities in Malformed Bind Request (LDAP Anonymous) is a Medium risk vulnerability that is one of the most frequently found on networks around the world. This issue has been around since at least 1990 but has proven either difficult to detect, difficult to resolve or prone to being overlooked entirely.

Vulnerability Name:Malformed Bind Request (LDAP Anonymous)
Test ID:1466
Risk:Medium
Category:Simple Network services
Type:Attack
Summary:
  • The Bind function in the Exchange Directory Service has an unchecked buffer that poses two threats to safe operation. The first is a denial of service threat. A malformed Bind request could overflow the buffer, causing the Exchange Directory service to crash. The server would not need to be rebooted, but the Exchange Directory service, and possibly dependent services as well, would need to be restarted in order to resume messaging service. The second threat is more esoteric and would be far more difficult to exploit. A carefully-constructed Bind request could cause arbitrary code to execute on the server via a classic buffer overrun technique. Neither attack could occur accidentally.
  • Customers who are using Exchange but who have turned off LDAP support in the Directory Service are not at risk from this vulnerability. Customers also can reduce their vulnerability to attacks from external sources by filtering incoming packets destined for TCP port 389, the LDAP service port.
  • Microsoft has no reports of any customers being affected by this vulnerability. However, Microsoft is proactively releasing a patch that corrects the problem.
  • Other servers, such as Sun One, also allow NULL binding which allows an attacker to connect to the LDAP server without providing any means of authentication.
Impact:Attackers can gain critical information about the host.
Solution:

http://www.microsoft.com/technet/security/bulletin/ms99-009.mspx

On newer versions of Windows (2003 and up), anonymous might have been re-enabled manually see: http://support.microsoft.com/default.aspx?scid=kb;EN-US;326690

For Sun ONE, see "Preventing Binds With No Password" section provided at:http://docs.oracle.com/cd/E19693-01/819-0998/gdrts/index.html

CVE:CVE-1999-0385
More Information:
Nist NVD (CVSS):AV:N/AC:L/Au:N/C:C/I:C/A:C
CVSS Score:10.0

Scanning for and Finding Vulnerabilities in Malformed Bind Request (LDAP Anonymous)

Use of Vulnerability Management tools are standard practice for the discovery of this vulnerability. The primary failure of VA in finding this vulnerability is related to setting the proper scope and frequency of network scans. It is vital that the broadest range of hosts (active IPs) possible are scanned and that scanning is done frequently. We recommend weekly. Your existing scanning solution or set of test tools should make this not just possible, but easy and affordable. 

Penetration Testing for LDAP

The Vulnerabilities in Malformed Bind Request (LDAP Anonymous) is prone to false positive reports by most vulnerability assessment solutions. AVDS is alone in using behavior based testing that eliminates this issue. For all other VA tools security consultants will recommend confirmation by direct observation. In any case Penetration testing procedures for discovery of Vulnerabilities in Malformed Bind Request (LDAP Anonymous) produces the highest discovery accuracy rate, but the infrequency of this expensive form of testing degrades its value. The ideal would be to have pentesting accuracy and the frequency and scope possibilities of VA solution.

Security Updates on Vulnerabilities in Malformed Bind Request (LDAP Anonymous)

Given that this is one of the most frequently found vulnerabilities, there is ample information regarding mitigation online and very good reason to get it fixed. Hackers are also aware that this is a frequently found vulnerability and so its discovery and repair is that much more important. It is so well known and common that any network that has it present and unmitigated indicates "low hanging fruit" to attackers.

Disclosures related to this vulnerability

http://securitysynapse.blogspot.com/2013/09/dangers-of-ldap-null-base-and-bind.html

Patching/Repairing this Vulnerability

https://technet.microsoft.com/en-us/library/security/ms99-009.aspx

Vulnerabilities in Malformed Bind Request (LDAP Anonymous) is a Medium risk vulnerability that is also high frequency and high visibility. This is the most severe combination of security factors that exists and it is extremely important to find it on your network and fix it as soon as possible.

Exploits related to Vulnerabilities in Malformed Bind Request (LDAP Anonymous)

 

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