CVE-2009-3767 in OpenLDAP
Summary
by MITRE
libraries/libldap/tls_o.c in OpenLDAP 2.2 and 2.4, and possibly other versions, when OpenSSL is used, does not properly handle a \0 character in a domain name in the subject s Common Name (CN) field of an X.509 certificate, which allows man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority, a related issue to CVE-2009-2408.
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Analysis
by VulDB Data Team • 08/24/2021
The vulnerability described in CVE-2009-3767 represents a critical security flaw in OpenLDAP's handling of X.509 certificate validation, specifically within the TLS implementation component. This issue affects OpenLDAP versions 2.2 and 2.4, with potential impacts extending to other versions that utilize OpenSSL for secure communications. The vulnerability stems from improper validation of domain names contained within the Common Name field of X.509 certificates, creating a significant attack vector for man-in-the-middle operations.
The technical flaw manifests when OpenLDAP processes X.509 certificates containing a null character within the subject's Common Name field. This null character injection allows attackers to craft malicious certificates that bypass normal certificate validation procedures, effectively enabling attackers to impersonate legitimate SSL servers. The vulnerability operates by exploiting the way OpenLDAP's TLS implementation handles string parsing and validation, particularly when comparing certificate subject names against expected domain values. This flaw directly relates to CVE-2009-2408, indicating a broader class of certificate validation issues within the OpenLDAP implementation.
The operational impact of this vulnerability is severe, as it undermines the fundamental security guarantees provided by SSL/TLS encryption. Attackers can exploit this weakness to perform successful man-in-the-middle attacks against OpenLDAP services, potentially intercepting sensitive authentication data, session information, and other confidential communications. The vulnerability is particularly dangerous because it allows attackers to spoof arbitrary SSL servers, meaning they can impersonate any legitimate server within the certificate authority's trust domain. This capability enables comprehensive data interception and modification attacks, potentially leading to complete system compromise and unauthorized access to protected resources.
Organizations using affected OpenLDAP versions should immediately implement mitigations including upgrading to patched versions of OpenLDAP, implementing additional certificate validation controls, and monitoring for suspicious certificate usage patterns. The vulnerability aligns with ATT&CK technique T1552.001 for credential access and T1041 for data encryption, while the CWE classification falls under CWE-295 for improper certificate validation. System administrators should also consider implementing certificate pinning mechanisms and additional network monitoring to detect potential exploitation attempts. The security community has documented similar vulnerabilities in other SSL/TLS implementations, emphasizing the importance of robust certificate validation procedures and the need for comprehensive security testing of cryptographic libraries.