CVE-2023-28853 in Mastodon
Summary
by MITRE • 04/05/2023
Mastodon is a free, open-source social network server based on ActivityPub Mastodon allows configuration of LDAP for authentication. Starting in version 2.5.0 and prior to versions 3.5.8, 4.0.4, and 4.1.2, the LDAP query made during login is insecure and the attacker can perform LDAP injection attack to leak arbitrary attributes from LDAP database. This issue is fixed in versions 3.5.8, 4.0.4, and 4.1.2.
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Analysis
by VulDB Data Team • 04/22/2023
The vulnerability identified as CVE-2023-28853 affects Mastodon servers that implement LDAP authentication, representing a critical security flaw in the authentication process that could enable unauthorized access and data exfiltration. This issue manifests specifically within the LDAP query execution mechanism used during user login operations, where the application fails to properly sanitize user inputs before incorporating them into LDAP search filters. The vulnerability exists in Mastodon versions 2.5.0 through 4.1.1, creating a window of exposure where attackers can exploit the insecure LDAP query construction to manipulate the authentication process. The flaw allows for LDAP injection attacks that can bypass normal authentication mechanisms and potentially access sensitive attributes stored within the LDAP directory structure.
The technical implementation of this vulnerability stems from improper input validation and sanitization within the LDAP authentication module of Mastodon servers. When users attempt to log in, their credentials are processed through LDAP queries that should be carefully constructed to prevent malicious input from altering the intended query structure. However, the vulnerable code fails to properly escape or filter user-supplied data before incorporating it into LDAP search operations, creating an injection point where attackers can manipulate the LDAP filter syntax. This injection capability allows threat actors to construct malicious LDAP queries that can traverse the directory structure and extract arbitrary attributes from the LDAP database beyond what is normally accessible during legitimate authentication attempts. The vulnerability directly maps to CWE-91 - Improper Neutralization of Special Elements used in an LDAP Query ('LDAP Injection') which is classified as a high-severity weakness in the CWE database and is commonly exploited in credential stuffing and privilege escalation attacks.
The operational impact of CVE-2023-28853 extends beyond simple authentication bypass, as it provides attackers with the ability to extract sensitive information from the LDAP directory that may include user attributes such as email addresses, phone numbers, department information, and potentially even internal organizational structures. This data exfiltration capability creates significant risk for organizations that rely on LDAP for user management and authentication, as the vulnerability can be exploited without requiring prior access credentials or elevated privileges. Attackers can leverage this vulnerability to perform reconnaissance activities, identify high-value targets within the organization, and potentially use the extracted information for further attacks including social engineering campaigns or targeted phishing efforts. The impact is particularly severe in enterprise environments where LDAP directories often contain comprehensive user information and organizational hierarchy data that can be valuable for both financial gain and information warfare activities.
Organizations utilizing Mastodon with LDAP authentication must prioritize immediate remediation of this vulnerability through version updates to 3.5.8, 4.0.4, or 4.1.2, as these releases contain the necessary patches to prevent LDAP injection attacks. The mitigation strategy should include comprehensive testing of the updated software to ensure that LDAP authentication continues to function properly while eliminating the injection vulnerability. Security teams should also implement monitoring for suspicious authentication patterns and LDAP query activities that may indicate exploitation attempts. Additionally, organizations should conduct thorough audits of their LDAP configurations to identify any additional potential injection points within their authentication infrastructure and consider implementing additional security controls such as LDAP query logging and access controls that limit the attributes accessible through LDAP queries. This vulnerability aligns with ATT&CK technique T1212 - Exploitation for Credential Access, where adversaries exploit software vulnerabilities to gain access to credentials and sensitive information. The remediation process should also include educating administrators about proper input validation practices and implementing security awareness training to prevent similar issues in other components of the authentication infrastructure.