CVE-2026-4583: MPOS M6 PLUS Auth Bypass Vulnerability

CVE-2026-4583 Overview

A vulnerability has been identified in the Shenzhen HCC Technology MPOS M6 PLUS mobile point-of-sale device running firmware version 1V.31-N. This authentication bypass vulnerability exists within the Bluetooth Handler component, allowing attackers to perform capture-replay attacks to circumvent authentication mechanisms. The attack requires adjacent network access (local Bluetooth range) and is considered to have high complexity, making exploitation difficult but still possible for determined attackers.

Critical Impact

Successful exploitation allows attackers within Bluetooth range to bypass authentication on the MPOS device through capture-replay attacks, potentially enabling unauthorized access to payment terminal functionality.

Affected Products

• Shenzhen HCC Technology MPOS M6 PLUS firmware version 1V.31-N

Discovery Timeline

• 2026-03-23 - CVE-2026-4583 published to NVD
• 2026-03-23 - Last updated in NVD database

Note: The vendor was contacted early about this disclosure but did not respond in any way.

Technical Details for CVE-2026-4583

Vulnerability Analysis

This vulnerability (CWE-287: Improper Authentication) affects the Bluetooth Handler component in the Shenzhen HCC Technology MPOS M6 PLUS device. The flaw allows authentication bypass through capture-replay techniques, where an attacker can intercept and replay Bluetooth authentication tokens or handshake data to gain unauthorized access without proper credentials.

The attack requires the adversary to be within adjacent network proximity (Bluetooth range) of the target device. While the exploitation is considered difficult due to high attack complexity, the vulnerability poses significant risks in environments where MPOS devices are used for payment processing, as unauthorized access could compromise transaction integrity.

Root Cause

The root cause of this vulnerability lies in the improper implementation of authentication mechanisms within the Bluetooth Handler component. The device fails to implement proper anti-replay protections, allowing captured authentication data to be reused in subsequent connection attempts. This lack of session uniqueness or timestamp validation in the Bluetooth pairing and authentication process enables the capture-replay attack vector.

Attack Vector

The attack vector is adjacent network-based, requiring the attacker to be within Bluetooth communication range of the target MPOS M6 PLUS device. The attack proceeds as follows:

1. The attacker positions themselves within Bluetooth range of the target device
2. Using Bluetooth sniffing tools, the attacker captures authentication handshake data during a legitimate connection
3. The attacker replays the captured authentication data to the device
4. Due to insufficient replay protection, the device accepts the replayed credentials and grants access

The vulnerability mechanism involves the Bluetooth Handler failing to validate the freshness or uniqueness of authentication tokens. Captured Bluetooth pairing or authentication packets can be replayed to establish unauthorized connections. For detailed technical analysis, refer to the GitHub CVE-2 Replay Exploit documentation.

Detection Methods for CVE-2026-4583

Indicators of Compromise

• Unexpected Bluetooth connection attempts or multiple rapid pairing requests to MPOS devices
• Bluetooth connection logs showing duplicate session identifiers or authentication tokens
• Unusual device behavior following Bluetooth connections from unknown or previously unpaired devices

Detection Strategies

• Monitor Bluetooth adapter logs for repeated connection attempts with identical authentication parameters
• Implement network monitoring solutions that can detect Bluetooth traffic anomalies in proximity to MPOS terminals
• Review device audit logs for authentication events occurring outside normal business hours or from unexpected locations

Monitoring Recommendations

• Deploy endpoint detection solutions capable of monitoring Bluetooth communication patterns on payment terminal infrastructure
• Establish baseline Bluetooth activity for MPOS devices and alert on deviations
• Consider implementing proximity detection to identify unauthorized devices within Bluetooth range of payment terminals

How to Mitigate CVE-2026-4583

Immediate Actions Required

• Disable Bluetooth functionality on affected MPOS M6 PLUS devices when not actively required for operation
• Implement physical security controls to limit unauthorized proximity to payment terminals
• Consider transitioning to alternative MPOS solutions until a vendor patch is available
• Conduct a security audit of all deployed M6 PLUS devices to identify potential compromise

Patch Information

No official patch is currently available from Shenzhen HCC Technology. The vendor was contacted early about this disclosure but did not respond in any way. Organizations using affected devices should implement compensating controls until a security update becomes available.

For additional information, consult the following resources:

• GitHub CVE-2 Replay Exploit
• VulDB #352420

Workarounds

• Disable Bluetooth on affected devices and use wired connections for data transfer where possible
• Implement strict physical access controls around MPOS device deployment areas
• Use Faraday cages or RF shielding in high-security environments to prevent Bluetooth interception
• Monitor for vendor updates and apply patches immediately when available

# Configuration example - Disable Bluetooth on device (if supported)
# Consult device documentation for specific commands
# General recommendation: Access device settings and disable Bluetooth radio
# Alternative: Implement physical controls or network segmentation