CVE-2026-15722 in Directory Server
Summary
by MITRE • 07/31/2026
A stack buffer overflow flaw was found in 389 Directory Server (389-ds-base). The get_ruvelement_from_berval() function in repl5_ruv.c copies digit characters from a network-supplied RUV berval into a fixed 16-byte stack buffer without bounds checking. A remote unauthenticated attacker can crash the LDAP server by sending a crafted StartNSDS50ReplicationRequest extended operation containing a replica ID field with more than 16 digit characters. The overflow occurs during payload decoding, before any authorization check. Stack protectors limit impact to denial of service.
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Analysis
by VulDB Data Team • 07/31/2026
The vulnerability under examination represents a critical stack buffer overflow flaw within the 389 Directory Server implementation that exposes a fundamental security weakness in the replication component. This issue resides in the repl5_ruv.c source file where the get_ruvelement_from_berval() function processes network-supplied data without proper bounds validation, creating an exploitable condition that can be triggered through crafted LDAP operations. The flaw specifically targets the handling of replica ID fields within StartNSDS50ReplicationRequest extended operations, demonstrating how seemingly benign input processing can lead to severe system instability.
The technical execution of this vulnerability occurs during the payload decoding phase of LDAP communication where the function blindly copies digit characters from a network-supplied berval structure into a fixed 16-byte stack buffer. This classic buffer overflow scenario demonstrates poor input validation practices that violate fundamental security principles outlined in CWE-121, which addresses stack-based buffer overflow conditions. The lack of bounds checking before memory copying operations creates an opportunity for attackers to overwrite adjacent stack memory locations, potentially leading to arbitrary code execution or system crash states.
The operational impact of this vulnerability extends beyond simple denial of service as it represents a pre-authentication attack vector that can be exploited by remote unauthenticated adversaries. This characteristic places the vulnerability in the category of high-severity issues that can be leveraged for system disruption without requiring any prior access credentials or authorization checks. The timing of the overflow during payload decoding means that attackers can cause immediate system instability before any authentication or authorization processes occur, making this particularly dangerous in production environments where LDAP services are exposed to external networks.
The use of stack protectors in the affected implementation limits the potential impact to denial of service conditions rather than full exploitation, but this mitigation is insufficient for maintaining system availability and integrity. This vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, and demonstrates how buffer overflow conditions can be weaponized for system disruption. Organizations implementing 389 Directory Server must recognize that this vulnerability represents a weakness in their directory service infrastructure that could be exploited to compromise service availability and potentially gain intelligence about the underlying system architecture through repeated attack attempts.
Mitigation strategies should focus on immediate patching of the 389 Directory Server software to address the buffer overflow condition in the repl5_ruv.c file, ensuring proper bounds checking is implemented for all network-supplied input data. Network segmentation and access control measures should be enhanced to limit exposure of LDAP services to untrusted networks, while monitoring systems should be configured to detect unusual patterns in replication request traffic that might indicate exploitation attempts. The vulnerability serves as a reminder of the critical importance of input validation and bounds checking in security-critical applications, particularly those handling network data in enterprise directory services environments where reliability and availability are paramount for business operations.