CVE-2025-20672: MediaTek MT7902 Privilege Escalation Flaw

CVE-2025-20672 Overview

CVE-2025-20672 is a critical heap buffer overflow vulnerability affecting the Bluetooth driver in multiple MediaTek wireless chipsets. The flaw stems from an incorrect bounds check that allows an out-of-bounds write operation, potentially enabling local privilege escalation. Attackers with user-level execution privileges can exploit this vulnerability without requiring any user interaction.

Critical Impact

This vulnerability allows local privilege escalation through a heap buffer overflow in the Bluetooth driver, potentially granting attackers elevated system access on devices using affected MediaTek wireless chipsets.

Affected Products

• MediaTek MT7902 and MT7902 Firmware
• MediaTek MT7921 and MT7921 Firmware
• MediaTek MT7922 and MT7922 Firmware
• MediaTek MT7925 and MT7925 Firmware
• MediaTek MT7927 and MT7927 Firmware

Discovery Timeline

• 2025-06-02 - CVE-2025-20672 published to NVD
• 2025-07-02 - Last updated in NVD database

Technical Details for CVE-2025-20672

Vulnerability Analysis

This vulnerability is classified as CWE-122 (Heap-based Buffer Overflow), a memory corruption issue where data is written beyond the allocated boundaries of a heap buffer. The root cause lies in the Bluetooth driver's improper bounds checking logic, which fails to adequately validate input sizes before performing write operations.

The vulnerability enables attackers to corrupt adjacent heap memory structures, potentially overwriting critical control data such as function pointers or object metadata. By carefully crafting malicious input, an attacker can manipulate program execution flow to gain elevated privileges on the target system.

What makes this vulnerability particularly concerning is that exploitation does not require user interaction. An attacker with standard user execution privileges can trigger the vulnerable code path and escalate their privileges without any action from the device user.

Root Cause

The vulnerability originates from an incorrect bounds check in the MediaTek Bluetooth driver firmware. The driver fails to properly validate the size of incoming data against the allocated buffer boundaries before writing to heap memory. This allows specially crafted input to exceed the expected buffer size, resulting in heap memory corruption.

The flawed bounds validation logic permits data larger than the allocated buffer to be written, overflowing into adjacent memory regions. This is a classic heap buffer overflow pattern where the comparison logic used for boundary checking contains an off-by-one error or uses an incorrect comparison operator.

Attack Vector

The attack can be initiated over a network connection (AV:N) and requires low complexity to execute. While the vulnerability description mentions local privilege escalation with user execution privileges, the network attack vector indicates the vulnerability can potentially be triggered remotely through Bluetooth communications.

The exploitation scenario involves:

1. An attacker sends malformed Bluetooth packets or data to a device with a vulnerable MediaTek wireless chipset
2. The Bluetooth driver processes the incoming data without adequate bounds checking
3. The oversized data overflows the allocated heap buffer, corrupting adjacent memory
4. The memory corruption is leveraged to hijack execution flow or modify security-critical data structures
5. The attacker gains elevated privileges on the target system

The vulnerability is particularly dangerous because it requires no user interaction and can be exploited by users with standard execution privileges.

Detection Methods for CVE-2025-20672

Indicators of Compromise

• Unexpected Bluetooth driver crashes or kernel panics related to mt79xx driver modules
• System log entries indicating heap corruption or memory access violations in Bluetooth-related processes
• Anomalous privilege changes for processes interacting with Bluetooth subsystems
• Unexpected memory allocation patterns in Bluetooth driver operations

Detection Strategies

• Monitor kernel logs for out-of-bounds memory access errors originating from MediaTek Bluetooth driver modules
• Implement endpoint detection rules to identify exploitation attempts targeting Bluetooth driver vulnerabilities
• Deploy SentinelOne Singularity platform to detect heap overflow exploitation patterns and privilege escalation attempts
• Utilize memory protection tools to detect heap buffer overflow exploitation in real-time

Monitoring Recommendations

• Enable verbose logging for Bluetooth subsystem events and driver operations
• Monitor for unusual Bluetooth connection patterns or malformed packet handling errors
• Track system processes for unexpected privilege escalation following Bluetooth activity
• Implement network segmentation to limit exposure of devices with vulnerable chipsets

How to Mitigate CVE-2025-20672

Immediate Actions Required

• Apply the security patch identified by Patch ID WCNCR00412257 from MediaTek immediately
• Review the MediaTek Security Bulletin June 2025 for detailed patching guidance
• Inventory all devices using affected MediaTek MT7902, MT7921, MT7922, MT7925, and MT7927 chipsets
• Prioritize patching for systems in high-risk environments or with sensitive data access

Patch Information

MediaTek has released a security patch to address this vulnerability. The fix is tracked internally as Patch ID WCNCR00412257 and Issue ID MSV-3292. Organizations should obtain the updated firmware from MediaTek or their device manufacturer.

The official security bulletin with patch details is available at the MediaTek Product Security Bulletin for June 2025. Device manufacturers incorporating affected MediaTek chipsets should integrate the updated driver firmware and push updates to their customers.

Workarounds

• Disable Bluetooth functionality on affected devices if not required for business operations
• Implement network segmentation to isolate devices with vulnerable chipsets from untrusted networks
• Restrict physical and network proximity access to devices with affected MediaTek wireless chipsets
• Deploy endpoint protection solutions like SentinelOne to detect and block exploitation attempts

# Example: Disable Bluetooth on Linux systems with affected MediaTek chipsets
sudo systemctl stop bluetooth
sudo systemctl disable bluetooth

# Blacklist the MediaTek Bluetooth driver module
echo "blacklist mt7921e" | sudo tee /etc/modprobe.d/disable-mt79xx-bt.conf
echo "blacklist mt7921u" | sudo tee -a /etc/modprobe.d/disable-mt79xx-bt.conf

# Apply changes
sudo update-initramfs -u