Overview
CVE-2025-65503 describes a use-after-free vulnerability discovered in Redboltz async_mqtt version 10.2.5. This vulnerability can be exploited by local users to trigger a denial-of-service (DoS) condition. The root cause lies in the improper destruction order of objects during error handling, specifically when SSL initialization fails.
Technical Details
The vulnerability stems from an incorrect destruction order between the io_context and endpoint objects within the Redboltz async_mqtt library. Specifically, if the SSL initialization process encounters a failure, the destruction order may not be properly synchronized. This leads to a situation where the io_context might be destroyed before the endpoint object, resulting in the endpoint object attempting to access freed memory during its own destruction. This memory access to freed memory triggers the use-after-free condition.
The trigger condition involves an SSL initialization failure. This can be artificially induced through misconfiguration or by deliberately providing invalid SSL parameters to the MQTT client.
CVSS Analysis
Currently, the CVE entry lists the severity as N/A and the CVSS score as N/A. While a CVSS score isn’t available, a use-after-free vulnerability can often have significant implications, potentially leading to:
- Denial of Service (DoS): The most likely outcome, as the program crashes due to accessing freed memory.
- Potential for Code Execution: Under certain conditions, a use-after-free vulnerability *could* be leveraged for arbitrary code execution, though this is highly dependent on the specific memory layout and exploit techniques. This would substantially increase the severity.
Until a formal CVSS score is assigned, treat this vulnerability with caution.
Possible Impact
The exploitation of CVE-2025-65503 can lead to a denial of service, potentially disrupting MQTT-based communication. This is particularly concerning for:
- IoT Devices: Devices relying on Redboltz async_mqtt for communication could become unresponsive.
- MQTT Brokers: A compromised MQTT client crashing due to this vulnerability could potentially destabilize or crash the MQTT broker itself, especially under high load or specific configurations.
- Applications relying on MQTT: Applications that depend on the MQTT broker may experience disruptions, leading to functionality loss.
Since the vulnerability can be triggered locally, systems that accept untrusted input to the MQTT client configuration are particularly vulnerable.
Mitigation and Patch Steps
The primary mitigation step is to update Redboltz async_mqtt to a version that includes the fix. According to the provided references, a fix has been implemented.
- Update async_mqtt: Upgrade to a version of Redboltz async_mqtt that includes the fix for issue #436. The pull request #437 likely contains the necessary patch.
- Review SSL Configuration: Carefully review the SSL configuration used by your async_mqtt client. Ensure that all parameters are valid and that the SSL certificate is properly configured. This will help prevent accidental triggering of the vulnerability.
- Input Validation: If the async_mqtt client’s SSL configuration is derived from user input, ensure thorough validation and sanitization to prevent malicious actors from injecting invalid parameters that could trigger the SSL initialization failure.
References
