Memory Exhaustion in 389 Directory Server

Detection Guidance

This vulnerability can be detected by monitoring the memory usage of the 389 Directory Server process, especially when the Content Synchronization persistent search plugin is in use. A significant and unbounded increase in memory consumption may indicate that an authenticated client has stopped reading sync responses, causing memory growth.

You can use system monitoring commands to observe memory usage and process behavior, such as:

• top or htop - to monitor real-time memory usage of the 389 Directory Server process.
• ps aux --sort=-rss | grep 389-ds-base - to check memory consumption of the server process.
• vmstat or free -m - to observe overall system memory usage trends.

Additionally, reviewing server logs for crashes or abnormal connection terminations related to the sync_persist plugin may help detect race condition issues.

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Mitigation Strategies

Immediate mitigation steps include limiting or disabling the use of the Content Synchronization persistent search plugin in the 389 Directory Server until a fix is available.

Monitoring and managing authenticated clients to ensure they properly consume sync responses can help prevent unbounded memory growth.

Regularly monitor server memory usage and restart the 389 Directory Server if excessive memory consumption or crashes occur.

Apply any patches or updates provided by the vendor once available, as no upstream fix was implemented as of April 22, 2026.

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Compliance Impact

The vulnerability in 389 Directory Server's Content Synchronization persistent search plugin primarily causes denial of service through unbounded memory growth and potential crashes. It does not directly impact confidentiality or integrity of data.

Since the vulnerability affects availability but does not involve unauthorized data access or modification, its impact on compliance with standards like GDPR or HIPAA—which emphasize data privacy and integrity—is indirect and limited.

However, availability is a component of many security frameworks, so prolonged denial of service could affect overall system reliability and availability requirements under certain regulations.

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Executive Summary

The vulnerability affects the 389 Directory Server's Content Synchronization persistent search plugin. It causes unbounded memory growth when an authenticated client starts a persistent sync search but then stops reading the sync responses. This leads to modification events accumulating indefinitely in memory, eventually exhausting server resources and causing a crash.

Additionally, there are race conditions in the plugin's thread lifecycle: a dangling pointer issue during connection termination and thread management problems during server shutdown. These can cause crashes or undefined behavior.

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Impact Analysis

This vulnerability can lead to denial of service (DoS) by exhausting server memory and causing crashes. An attacker or malfunctioning client that stops reading sync responses can cause the server to consume increasing amounts of memory, eventually making the service unavailable.

Furthermore, race conditions in thread management can cause instability or crashes during connection teardown or server shutdown, impacting availability and reliability.

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