CVE-2020-16093 in lemonldap-ng
Summary
by MITRE • 07/18/2022
In LemonLDAP::NG (aka lemonldap-ng) through 2.0.8, validity of the X.509 certificate is not checked by default when connecting to remote LDAP backends, because the default configuration of the Net::LDAPS module for Perl is used.
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Analysis
by VulDB Data Team • 08/01/2022
LemonLDAP::NG represents a comprehensive single sign-on solution that facilitates centralized authentication across multiple applications and services. The software operates as an identity provider and implements various authentication mechanisms including LDAP integration for backend user management. This particular vulnerability exists within the LDAP connection handling mechanism of the system's Perl-based components. The default configuration of the Net::LDAPS module within the Perl environment fails to validate X.509 certificate authenticity during secure LDAP connections to remote servers. This oversight creates a critical security gap that allows attackers to potentially perform man-in-the-middle attacks against the authentication infrastructure.
The technical flaw stems from the improper handling of SSL/TLS certificate validation within the Net::LDAPS module usage. When LemonLDAP::NG establishes connections to remote LDAP servers using LDAPS protocol, it relies on the default Perl module behavior which does not enforce certificate validation by default. This configuration allows connections to proceed even when the remote server presents a certificate that is invalid, expired, self-signed, or otherwise untrusted. The vulnerability specifically affects versions through 2.0.8, indicating that this was a known issue within the software stack that required explicit configuration changes to address. The flaw aligns with CWE-295, which addresses improper certificate validation in security protocols, and represents a failure in secure communication implementation.
The operational impact of this vulnerability is significant for organizations relying on LemonLDAP::NG for authentication services. An attacker positioned within the network or able to intercept traffic can potentially impersonate LDAP servers and gain unauthorized access to user credentials or authentication data. This compromises the entire authentication infrastructure since the system accepts connections from unverified certificate authorities. The vulnerability affects both the integrity and confidentiality of authentication communications, potentially allowing credential theft, session hijacking, or unauthorized access to protected resources. Organizations using this software without proper certificate validation configuration are exposed to attacks targeting their authentication systems, which could lead to broader security breaches within their IT environments.
Mitigation strategies should focus on explicitly configuring certificate validation within the Net::LDAPS module settings. System administrators must modify the LemonLDAP::NG configuration to enforce certificate verification during LDAP connections, typically by setting appropriate SSL/TLS options within the Perl module. Organizations should implement certificate pinning where possible, establish proper certificate management procedures, and regularly audit their authentication infrastructure. The solution involves updating the software configuration to disable insecure default behaviors and enable proper certificate validation. This remediation aligns with ATT&CK technique T1552.001 for credential access and T1046 for network service scanning, as the vulnerability enables attackers to establish unauthorized connections and potentially escalate privileges through compromised authentication systems. Regular security updates and configuration reviews are essential to maintain proper certificate validation practices and prevent exploitation of this vulnerability.