Executive Summary

CVE-2025-53114 is a vulnerability in the CometD library affecting multiple versions from 5.0.0 through 8.0.8. The issue arises when malicious or bad clients send a fixed batch value repeatedly while the server uses the acknowledgement extension. This causes the server's unacknowledged message queue to grow without bound, eventually leading to an OutOfMemoryError (OOM) on the server.

The root cause is that the server retains messages waiting for acknowledgment, but if clients do not properly acknowledge messages and keep sending the same batch value, the queue never clears. This uncontrolled resource consumption can crash the server.

The vulnerability has been patched in versions 5.0.23, 6.0.19, 7.0.19, and 8.0.9. As a temporary workaround, disabling the acknowledgement extension can prevent the issue.

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Impact Analysis

This vulnerability primarily impacts the availability of the CometD server. A single malicious client can cause the server's memory to be exhausted by forcing the unacknowledged message queue to grow indefinitely.

The resulting OutOfMemoryError can cause the server to crash or become unresponsive, leading to denial of service (DoS) conditions.

There is no direct impact on confidentiality or integrity, but the service disruption can affect users relying on the messaging system.

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Detection Guidance

This vulnerability can be detected by monitoring the CometD server for unusually high memory usage or OutOfMemoryError events caused by the unacknowledged message queue growing indefinitely.

A practical detection method involves analyzing heap dumps to identify if a large portion of memory is consumed by ServerSessionImpl objects retaining large queues of unacknowledged ServerMessageImpl objects, which indicates stalled message acknowledgments.

Additionally, monitoring for clients that consistently send a fixed batch value in the acknowledgement extension can help identify malicious or misbehaving clients.

While specific commands are not provided in the resources, typical commands to detect such issues include:

• Using Java tools like jcmd or jmap to generate heap dumps: `jcmd <pid> GC.heap_dump <file>` or `jmap -dump:format=b,file=<file> <pid>`
• Analyzing heap dumps with tools such as Eclipse MAT (Memory Analyzer Tool) to inspect the memory retained by ServerSessionImpl and ServerMessageImpl objects.
• Monitoring JVM logs for OutOfMemoryError occurrences.
• Using network monitoring tools or application logs to detect clients repeatedly sending fixed batch values in acknowledgement messages.

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Mitigation Strategies

Immediate mitigation steps include upgrading CometD to a patched version where the vulnerability is fixed.

• Upgrade to CometD versions 5.0.23, 6.0.19, 7.0.19, or 8.0.9 or later, which contain patches addressing this issue.
• As a workaround, disable the acknowledgement extension in the CometD server configuration to prevent the unacknowledged message queue from growing indefinitely.

These steps help prevent malicious clients from causing OutOfMemoryError conditions by exploiting the acknowledgement extension.

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Compliance Impact

The vulnerability primarily impacts availability by causing an OutOfMemoryError due to uncontrolled resource consumption when malicious clients exploit the acknowledgement extension. It does not affect confidentiality or integrity of data.

Since the vulnerability does not lead to data breaches or unauthorized data access, it does not directly impact compliance with data protection regulations such as GDPR or HIPAA, which focus on confidentiality and integrity of personal or sensitive information.

However, the resulting server outages caused by this vulnerability could indirectly affect compliance by disrupting availability requirements or service continuity obligations under certain standards.

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