CVE-2013-4449 in OpenLDAP
Summary
by MITRE
The rwm overlay in OpenLDAP 2.4.23, 2.4.36, and earlier does not properly count references, which allows remote attackers to cause a denial of service (slapd crash) by unbinding immediately after a search request, which triggers rwm_conn_destroy to free the session context while it is being used by rwm_op_search.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 02/01/2022
The vulnerability identified as CVE-2013-4449 affects the rwm overlay functionality within OpenLDAP versions 2.4.23, 2.4.36, and earlier. This issue represents a critical flaw in the reference counting mechanism that governs how the rwm overlay manages session contexts during LDAP operations. The rwm overlay, which stands for "reverse write mapping," is designed to provide a mechanism for mapping operations from one LDAP server to another while maintaining consistent session state. The vulnerability manifests when a remote attacker exploits a race condition in the reference counting logic that occurs during the cleanup phase of LDAP session management.
The technical flaw stems from improper reference counting implementation within the rwm overlay module. When a client performs a search operation and immediately unbinds from the LDAP server, the system enters a state where the rwm_conn_destroy function attempts to free the session context while it is still actively being referenced by the rwm_op_search function. This creates a classic use-after-free condition where memory that has been deallocated is still being accessed, leading to unpredictable behavior and ultimately causing the slapd daemon to crash. The vulnerability specifically targets the interaction between the connection destruction and search operation functions, where the reference count management fails to properly synchronize these operations.
The operational impact of this vulnerability is significant as it enables remote attackers to perform denial of service attacks against OpenLDAP servers running affected versions. An attacker requires only network access to the LDAP server to exploit this vulnerability, making it particularly dangerous in production environments where LDAP services are critical for authentication and directory operations. The crash results in complete service disruption, requiring system administrators to restart the slapd service and potentially causing cascading failures in applications that depend on LDAP authentication. This vulnerability can be exploited repeatedly, allowing attackers to maintain persistent denial of service conditions without requiring authentication credentials.
Mitigation strategies for CVE-2013-4449 involve immediate patching of affected OpenLDAP installations to versions that contain the corrected reference counting implementation. System administrators should also implement network-level controls to restrict LDAP access to trusted sources and monitor for unusual connection patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-415, which describes improper handling of reference counts leading to use-after-free conditions, and maps to ATT&CK technique T1499.004 for denial of service attacks. Organizations should also consider implementing intrusion detection systems that can identify the specific patterns associated with this vulnerability and establish incident response procedures to quickly address any exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to ensure that all LDAP services remain protected against similar memory management flaws.