CVE-2026-78701 in 389-ds-base
Summary
by MITRE • 08/25/2026
A flaw was found in 389-ds-base. A remote, authenticated attacker could exploit a vulnerability in the Simple Authentication and Security Layer (SASL) UNBIND process. By sending a specially crafted request, the attacker can cause a connection to stall, leading to resource exhaustion and a Denial of Service (DoS) for the server.
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Analysis
by VulDB Data Team • 08/25/2026
The 389 Directory Server is an open-source LDAP implementation widely used in enterprise environments for identity management and directory services. A critical vulnerability has been identified within its Simple Authentication and Security Layer, specifically affecting the UNBIND process which is responsible for terminating client connections. This flaw allows a remote attacker who possesses valid authentication credentials to exploit the server's connection handling logic. By sending a specially crafted request during this termination phase, the attacker can trigger an abnormal state in the server's processing pipeline that prevents the normal closure of the session and associated resources.
The technical nature of this vulnerability centers on improper resource cleanup or synchronization errors within the SASL UNBIND mechanism. When the maliciously constructed packet is received, the server fails to properly release internal locks or memory buffers allocated for the connection context. This leads to a stall in the processing thread responsible for that specific client session. Because directory servers often handle thousands of concurrent connections using multi-threaded architectures, such stalls can accumulate rapidly if an attacker targets multiple sessions simultaneously. The inability to complete the unbind operation effectively traps server resources, preventing them from being reused or freed up for other legitimate users.
The operational impact of this flaw is a significant Denial of Service condition against the 389 Directory Server infrastructure. As more connections are stalled due to crafted UNBIND requests, the server's available thread pool and memory capacity diminish progressively. This resource exhaustion results in degraded performance for all authenticated users attempting to query or modify directory data. In severe cases, the server may become unresponsive entirely, requiring a manual restart to restore service availability. Since exploitation requires authentication, this vulnerability is particularly dangerous in environments where internal network access grants LDAP credentials, allowing insider threats or compromised accounts to disrupt critical identity services without needing external network penetration.
From a classification perspective, this issue aligns with CWE-400 Uncontrolled Resource Consumption and CWE-787 Out-of-bounds Write if the stall involves memory corruption leading to instability. In terms of attack tactics, it corresponds to MITRE ATT&CK technique T1499 Endpoint Denial of Service, specifically through resource exhaustion via application layer protocols. The vulnerability highlights the importance of robust state management in directory server implementations and underscores the risks associated with complex authentication mechanisms like SASL when not properly hardened against malformed inputs during session teardown phases.
Mitigation strategies should prioritize applying vendor-provided patches that address the specific logic error in the UNBIND handler. Administrators must ensure their 389-ds-base packages are updated to versions where this flaw is resolved. In addition to patching, implementing network-level access controls can limit exposure by restricting LDAP traffic to trusted subnets and enforcing strict authentication policies. Monitoring tools should be configured to detect unusual patterns of connection termination failures or spikes in resource usage that may indicate an ongoing exploitation attempt. Regular audits of SASL configuration settings and adherence to least-privilege principles for directory accounts further reduce the attack surface available to potential adversaries seeking to disrupt service availability through this specific vector.