CVE-2026-16560 in Directory Server
Summary
by MITRE • 07/22/2026
A heap-buffer-overflow flaw was found in Directory Server (389-ds-base). When a DN contains a legacy-quoted value, the server won't close the heap allocation allowing another call to refer to the same memory pointer causing a denial of service or an arbitrary memory write operation.
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Analysis
by VulDB Data Team • 07/22/2026
The heap buffer overflow vulnerability identified in 389-ds-base directory server represents a critical memory management flaw that stems from improper handling of distinguished name (DN) parsing operations. This vulnerability exists within the server's processing of legacy-quoted values in DNs, where the system fails to properly terminate or release heap allocated memory structures. The flaw specifically manifests when the directory server encounters a DN containing a legacy-quoted value, creating a scenario where memory allocation remains active beyond its intended scope. This improper memory management creates a persistent memory pointer that subsequent operations can reference, fundamentally compromising the server's memory integrity and operational stability.
The technical execution of this vulnerability occurs during the DN parsing phase when the server processes legacy-quoted values within distinguished names. The underlying issue resides in the memory allocation routines that fail to properly close or deallocate heap memory spaces after initial processing of these specific DN formats. When a second call attempts to access the same memory region, the server can either experience a denial of service condition due to memory corruption or potentially execute an arbitrary memory write operation. This dual nature of impact makes the vulnerability particularly dangerous as it can be leveraged for both availability disruption and potential code execution scenarios.
The operational impact of this heap buffer overflow vulnerability extends beyond simple service disruption to encompass broader security implications within directory services infrastructure. Directory servers serve as critical components in identity management and authentication systems, making this vulnerability particularly concerning for organizations relying on 389-ds-base for their directory services. The denial of service aspect can effectively disable authentication services, while the arbitrary memory write capability could potentially allow attackers to manipulate server memory contents, leading to privilege escalation or information disclosure. This vulnerability directly violates security principles related to memory safety and resource management that are fundamental to secure system design.
Mitigation strategies for this heap buffer overflow vulnerability should focus on immediate patch application from vendor sources, as well as implementing comprehensive memory management validation procedures within directory server configurations. The fix typically involves ensuring proper deallocation of heap memory structures when processing legacy-quoted DN values, preventing subsequent calls from accessing stale memory pointers. Security teams should implement monitoring for abnormal memory usage patterns and consider deploying intrusion detection systems that can identify potential exploitation attempts targeting this specific memory corruption scenario. Organizations should also review their directory service configurations to minimize exposure to potentially malicious DN inputs and establish robust memory integrity checking mechanisms.
This vulnerability aligns with CWE-121 heap-based buffer overflow classification and demonstrates characteristics consistent with ATT&CK technique T1059.007 for command and scripting interpreter execution through memory corruption. The flaw represents a classic example of improper resource management where the system fails to properly manage allocated memory spaces, creating persistent memory references that can be exploited by malicious actors. The vulnerability's impact is amplified in environments where directory servers handle untrusted input from multiple sources, making it particularly relevant for enterprise security architectures relying on LDAP directory services for authentication and authorization functions.