CVE-2026-4736: Echo-Mate Information Disclosure Flaw

CVE-2026-4736 Overview

An Improper Handling of Values vulnerability has been identified in No-Chicken Echo-Mate, specifically affecting the SDK/rv1106-sdk/sysdrv/source/kernel/include/net/netfilter modules. This vulnerability is associated with program files nf_tables.h, nft_byteorder.c, and nft_meta.c. The flaw exists in the kernel-level netfilter implementation, which is responsible for packet filtering, network address translation, and other packet mangling operations.

Critical Impact

Local attackers with low privileges can exploit improper value handling in netfilter modules to potentially achieve high impact on confidentiality, integrity, and availability of both the vulnerable system and adjacent connected systems.

Affected Products

• No-Chicken Echo-Mate versions before V250329
• Echo-Mate SDK/rv1106-sdk kernel netfilter modules
• Systems utilizing nf_tables.h, nft_byteorder.c, and nft_meta.c components

Discovery Timeline

• 2026-03-24 - CVE-2026-4736 published to NVD
• 2026-03-24 - Last updated in NVD database

Technical Details for CVE-2026-4736

Vulnerability Analysis

This vulnerability falls under CWE-229 (Improper Handling of Values), indicating that the affected netfilter modules do not properly validate, sanitize, or process certain values during packet filtering operations. The flaw resides within core kernel networking components that handle network filtering and packet manipulation.

The vulnerability requires local access to exploit but presents a significant risk once an attacker has initial access to the system. When exploited, an attacker can potentially compromise the confidentiality, integrity, and availability of both the vulnerable system and connected systems in scope, making this a serious concern for embedded device deployments using the Echo-Mate SDK.

Root Cause

The root cause stems from improper handling of values within the netfilter subsystem components. Specifically, the vulnerability affects the nf_tables.h header file along with implementation files nft_byteorder.c and nft_meta.c. These components are critical for the kernel's packet filtering infrastructure and handle byte ordering conversions and metadata operations for network packets.

When values are not properly validated or handled within these netfilter modules, it can lead to unexpected behavior that attackers may leverage to compromise system security. The rv1106-sdk kernel implementation appears to contain inadequate value handling that differs from expected behavior in these critical networking components.

Attack Vector

The attack requires local access to the target system. An attacker with low-privilege access on a device running vulnerable Echo-Mate firmware can potentially exploit the improper value handling in the netfilter modules. While the attack complexity is considered high, successful exploitation does not require user interaction.

The vulnerability mechanism involves malformed or specially crafted values being processed by the netfilter kernel modules. Since these components operate at the kernel level, successful exploitation could lead to privilege escalation, kernel memory corruption, or other security-relevant impacts. The extended scope of this vulnerability means that successful exploitation can affect resources beyond the security scope of the vulnerable component, potentially impacting connected systems.

For technical details on the specific implementation changes, refer to the GitHub Pull Request addressing this issue.

Detection Methods for CVE-2026-4736

Indicators of Compromise

• Unexpected kernel panics or crashes related to netfilter operations
• Anomalous network filtering behavior or packet handling errors
• Unusual kernel log entries referencing nf_tables, nft_byteorder, or nft_meta modules
• Unexplained privilege escalation attempts on Echo-Mate devices

Detection Strategies

• Monitor kernel logs for errors originating from netfilter subsystem components
• Implement integrity monitoring on critical kernel module files (nft_byteorder.c, nft_meta.c)
• Deploy network anomaly detection to identify unusual packet filtering behavior
• Utilize SentinelOne's kernel-level monitoring capabilities to detect exploitation attempts

Monitoring Recommendations

• Enable comprehensive kernel logging for netfilter operations on affected Echo-Mate devices
• Implement file integrity monitoring for the SDK kernel components
• Monitor system call patterns for anomalous netfilter-related activity
• Establish baseline network filtering behavior to detect deviations indicative of exploitation

How to Mitigate CVE-2026-4736

Immediate Actions Required

• Update Echo-Mate firmware to version V250329 or later immediately
• Restrict local access to affected devices to trusted users only
• Implement defense-in-depth measures to limit the impact of potential exploitation
• Review and audit local user permissions on affected embedded systems

Patch Information

No-Chicken has addressed this vulnerability in Echo-Mate version V250329. The fix addresses the improper value handling issues within the netfilter kernel modules. Organizations should update to the patched version as soon as possible. The patch details are available in the GitHub Pull Request #8 for the Echo-Mate project.

Workarounds

• Limit local access to affected devices to only essential personnel until patching is complete
• Implement network segmentation to isolate affected Echo-Mate devices from critical systems
• Enable additional logging and monitoring on affected systems to detect exploitation attempts
• Consider disabling non-essential netfilter functionality if operationally feasible

# Verify current Echo-Mate firmware version
cat /etc/version || cat /proc/version

# Check for vulnerable netfilter modules
find /lib/modules -name "nft_*.ko" -exec modinfo {} \;

# Monitor kernel logs for netfilter-related errors
dmesg | grep -i "nf_tables\|nft_"