CVE-2025-5868: RT-Thread Buffer Overflow Vulnerability

CVE-2025-5868 Overview

A critical vulnerability has been discovered in RT-Thread 5.1.0, a popular real-time operating system designed for embedded systems and IoT devices. The vulnerability exists in the sys_thread_sigprocmask function within the file rt-thread/components/lwp/lwp_syscall.c. This flaw involves improper validation of an array index through manipulation of the how argument, which can lead to memory corruption and potentially arbitrary code execution.

Critical Impact

This vulnerability allows an attacker with local access and low privileges on an adjacent network to potentially achieve high impact on confidentiality, integrity, and availability of affected systems. Given RT-Thread's widespread use in IoT and embedded devices, successful exploitation could compromise critical infrastructure components.

Affected Products

• RT-Thread version 5.1.0
• RT-Thread LWP (Light Weight Process) component
• Embedded systems and IoT devices running affected RT-Thread versions

Discovery Timeline

• 2025-06-09 - CVE-2025-5868 published to NVD
• 2025-07-11 - Last updated in NVD database

Technical Details for CVE-2025-5868

Vulnerability Analysis

The vulnerability resides in the signal handling subsystem of RT-Thread's Light Weight Process (LWP) component. Specifically, the sys_thread_sigprocmask function fails to properly validate the how argument before using it as an index into an array. This improper validation of array index (CWE-129) combined with improper restriction of operations within memory buffer bounds (CWE-119) creates a dangerous condition where attackers can manipulate memory access patterns.

The sys_thread_sigprocmask function is part of the syscall interface that allows user-space processes to modify the signal mask for threads. When the how parameter is not properly validated, an attacker can supply an out-of-bounds value that leads to accessing memory outside the intended array boundaries.

Root Cause

The root cause of this vulnerability is the absence of proper bounds checking on the how argument in the sys_thread_sigprocmask function. The how parameter typically accepts values like SIG_BLOCK, SIG_UNBLOCK, and SIG_SETMASK, but the function does not validate that the supplied value falls within this expected range before using it as an array index. This allows an attacker to provide arbitrary values that result in out-of-bounds memory access.

Attack Vector

The vulnerability requires adjacent network access with low privileges and no user interaction. An attacker positioned on the same network segment as the vulnerable device could exploit this flaw through a malicious application or compromised process running on the RT-Thread system.

The attack involves crafting a syscall to sys_thread_sigprocmask with a malicious how value. Since the function lacks proper input validation, the crafted value bypasses any intended constraints and causes the system to access memory at unintended locations. This can lead to information disclosure, denial of service, or potentially arbitrary code execution depending on the memory layout and exploitation technique employed.

For detailed technical information about this vulnerability, see the GitHub Issue Discussion and VulDB entry #311627.

Detection Methods for CVE-2025-5868

Indicators of Compromise

• Unexpected crashes or system instability in RT-Thread-based devices
• Anomalous syscall patterns targeting sys_thread_sigprocmask with unusual how parameter values
• Memory corruption artifacts or unexpected memory access patterns in system logs
• Unusual process behavior related to signal handling operations

Detection Strategies

• Monitor syscall activity for sys_thread_sigprocmask invocations with out-of-bounds how parameter values
• Implement runtime integrity checking for the LWP component memory regions
• Deploy endpoint detection solutions capable of monitoring embedded system behavior for anomalous memory access patterns
• Use firmware integrity verification to detect unauthorized modifications to RT-Thread binaries

Monitoring Recommendations

• Enable verbose logging for syscall operations in RT-Thread deployments where supported
• Implement network segmentation to limit adjacent network access to critical embedded devices
• Monitor for unusual network traffic patterns targeting RT-Thread-based IoT devices
• Establish baseline behavior profiles for embedded systems to detect deviations indicative of exploitation attempts

How to Mitigate CVE-2025-5868

Immediate Actions Required

• Identify all RT-Thread 5.1.0 deployments in your environment and prioritize them for patching
• Implement network segmentation to isolate affected devices from untrusted network segments
• Restrict local access and privileges on systems running vulnerable RT-Thread versions
• Monitor the RT-Thread GitHub repository for official patch releases

Patch Information

Organizations should monitor the official RT-Thread project for security updates addressing this vulnerability. Check the RT-Thread GitHub Issues for the latest information on patches and remediation guidance. Apply vendor-provided patches as soon as they become available, following proper testing procedures for embedded system updates.

Workarounds

• Restrict network access to affected devices by implementing strict network segmentation and firewall rules
• Limit local user privileges on affected systems to reduce the attack surface
• Disable or restrict access to the LWP syscall interface if not required for your application
• Consider implementing custom input validation at the application layer for signal handling operations
• Deploy compensating controls such as intrusion detection systems to monitor for exploitation attempts

# Configuration example
# Network isolation for RT-Thread devices (example iptables rules)
# Restrict adjacent network access to critical embedded systems
iptables -A INPUT -i eth0 -s 192.168.1.0/24 -j DROP
iptables -A INPUT -i eth0 -s trusted_management_ip -j ACCEPT

# Monitor syscall activity (if logging is available)
# Check RT-Thread configuration for enabling syscall logging
# RT_USING_LOGTRACE=y in rtconfig.h for enhanced logging