CVE-2026-4737: Echo-Mate Use After Free Vulnerability

CVE-2026-4737 Overview

A Use After Free (UAF) vulnerability has been identified in the No-Chicken Echo-Mate device firmware, specifically within the SDK/rv1106-sdk/sysdrv/source/kernel/mm modules. The vulnerability is associated with program files in rmap.c, which handles reverse mapping operations in the kernel memory management subsystem. This type of vulnerability occurs when memory is accessed after it has been freed, potentially allowing attackers to execute arbitrary code or cause system instability.

Critical Impact

Local attackers with low privileges can exploit this Use After Free vulnerability to potentially achieve code execution with elevated privileges, compromise system integrity, and affect other components in the system scope.

Affected Products

• No-Chicken Echo-Mate firmware versions before V250329
• SDK/rv1106-sdk kernel memory management modules
• Devices utilizing the rv1106 system-on-chip platform

Discovery Timeline

• 2026-03-24 - CVE-2026-4737 published to NVD
• 2026-03-24 - Last updated in NVD database

Technical Details for CVE-2026-4737

Vulnerability Analysis

This Use After Free vulnerability resides in the kernel memory management subsystem of the Echo-Mate firmware, specifically within the rmap.c file that implements reverse mapping functionality. Reverse mapping (rmap) is a critical kernel mechanism that tracks which page table entries point to each physical page, enabling efficient page reclamation and copy-on-write operations.

The vulnerability requires local access to the system with low privileges to exploit. Despite the local attack vector, the potential impact is significant as successful exploitation could lead to high confidentiality, integrity, and availability impacts on both the vulnerable system and potentially other system components within scope.

Root Cause

The root cause of CVE-2026-4737 lies in improper memory lifecycle management within the rmap.c memory management module. Use After Free vulnerabilities (CWE-416) typically occur when:

1. Memory is allocated for a data structure
2. The memory is freed but a pointer to that memory is retained
3. The freed memory is subsequently accessed through the dangling pointer

In the context of the rv1106 SDK kernel modules, this occurs in the reverse mapping code path where memory references are not properly invalidated after deallocation, leaving dangling pointers that can be dereferenced during subsequent memory operations.

Attack Vector

The attack vector for this vulnerability is local, meaning an attacker would need to have some level of access to the affected system. The exploitation requires:

• Local Access: Physical or logical access to the Echo-Mate device
• Low Privileges: Only minimal user privileges are required to trigger the vulnerability
• No User Interaction: The vulnerability can be exploited without requiring any action from a legitimate user

An attacker could craft a sequence of memory operations that trigger the vulnerable code path in rmap.c, causing the system to access freed memory. By carefully controlling the contents of the reallocated memory region, the attacker could potentially redirect execution flow or corrupt critical kernel data structures.

Detection Methods for CVE-2026-4737

Indicators of Compromise

• Unexpected kernel panics or system crashes related to memory management operations
• Anomalous memory allocation patterns in kernel logs referencing rmap.c or memory mapping functions
• Signs of privilege escalation attempts from low-privileged processes
• Unusual process behavior following memory-intensive operations on the rv1106 platform

Detection Strategies

• Monitor kernel logs for memory corruption indicators such as use-after-free warnings or page fault errors in the mm subsystem
• Implement runtime memory sanitization tools (if available for the embedded platform) to detect UAF conditions
• Deploy endpoint detection solutions capable of monitoring kernel-level memory operations for anomalous patterns
• Track firmware versions across deployed Echo-Mate devices to identify unpatched systems

Monitoring Recommendations

• Enable verbose kernel logging for memory management subsystem events
• Implement centralized log collection for Echo-Mate devices to correlate potential exploitation attempts
• Set up alerts for unexpected device reboots or kernel crashes that may indicate exploitation attempts
• Regularly audit device firmware versions against known vulnerable releases

How to Mitigate CVE-2026-4737

Immediate Actions Required

• Update No-Chicken Echo-Mate firmware to version V250329 or later immediately
• Restrict local access to Echo-Mate devices to only authorized personnel and processes
• Implement network segmentation to limit potential lateral movement if a device is compromised
• Review access logs for any suspicious local activity on affected devices

Patch Information

The vulnerability has been addressed in Echo-Mate firmware version V250329. Technical details regarding the fix can be found in the GitHub Pull Request #9 for the Echo-Mate project. Organizations should prioritize updating all affected devices to the patched firmware version.

Workarounds

• If immediate patching is not possible, restrict local shell access to Echo-Mate devices
• Implement strict access controls limiting which users and processes can interact with the device
• Monitor affected devices more closely for signs of exploitation until patching can be completed
• Consider temporarily isolating vulnerable devices from production networks if they cannot be immediately patched

# Verify current Echo-Mate firmware version
# Ensure version is V250329 or later to confirm patched status
cat /etc/firmware_version

# If vulnerable, update firmware following vendor procedures
# Restrict local access until patching is complete
chmod 700 /dev/mm_*