CVE-2026-20407: Mediatek Nbiot SDK Privilege Escalation

CVE-2026-20407 Overview

CVE-2026-20407 is an out-of-bounds write vulnerability in MediaTek's WLAN STA (Station) driver that enables local privilege escalation. The vulnerability stems from a missing bounds check in the wireless driver, allowing attackers with user-level execution privileges to escalate to higher privileges without requiring user interaction.

This critical vulnerability (CWE-787: Out-of-Bounds Write) affects multiple MediaTek wireless chipsets commonly found in laptops, IoT devices, and mobile platforms. The lack of proper boundary validation in the driver allows memory corruption that can be leveraged to gain elevated system access.

Critical Impact

Local attackers can achieve privilege escalation from user context to higher privileges, potentially compromising system integrity and confidentiality across affected MediaTek wireless chipsets.

Affected Products

• MediaTek NB-IoT SDK
• MediaTek MT7902
• MediaTek MT7920
• MediaTek MT7921
• MediaTek MT7922
• MediaTek MT7925
• MediaTek MT7927

Discovery Timeline

• 2026-02-02 - CVE-2026-20407 published to NVD
• 2026-02-04 - Last updated in NVD database

Technical Details for CVE-2026-20407

Vulnerability Analysis

The vulnerability exists within the MediaTek WLAN STA driver, a kernel-level component responsible for managing wireless station mode connectivity. The missing bounds check allows writes beyond the intended memory buffer boundaries, enabling memory corruption that can be weaponized for privilege escalation.

The attack vector is local, meaning an attacker must have existing access to the system to exploit this vulnerability. However, no user privileges are required to initiate the attack, and no user interaction is needed for successful exploitation. The scope of the vulnerability extends beyond the vulnerable component, allowing impact on system confidentiality, integrity, and availability.

The affected MediaTek chipsets (MT7902, MT7920, MT7921, MT7922, MT7925, MT7927) are widely deployed in consumer laptops, embedded systems, and IoT devices, significantly expanding the potential attack surface.

Root Cause

The root cause is a missing bounds check (CWE-787) in the WLAN STA driver code path. When processing certain wireless-related data structures or operations, the driver fails to validate that data being written stays within allocated buffer boundaries. This allows an attacker to craft malicious input that triggers an out-of-bounds write, corrupting adjacent memory regions.

Out-of-bounds write vulnerabilities in kernel drivers are particularly dangerous because they operate in privileged kernel context. Memory corruption at this level can overwrite critical kernel structures, function pointers, or security mechanisms, facilitating complete system compromise.

Attack Vector

The attack is performed locally on the target system. An attacker with user-level execution privileges can interact with the vulnerable WLAN driver through standard system interfaces. By providing specially crafted input that bypasses the missing bounds validation, the attacker can trigger the out-of-bounds write condition.

The exploitation does not require user interaction, making it suitable for automated attacks or malware that has gained initial foothold on a system. Once the out-of-bounds write is achieved, the attacker can manipulate kernel memory to escalate privileges, potentially gaining root or system-level access.

The vulnerability is tracked internally by MediaTek as Patch ID: WCNCR00464377 and Issue ID: MSV-4905.

Detection Methods for CVE-2026-20407

Indicators of Compromise

• Unexpected kernel crashes or system instability related to wireless driver operations
• Anomalous memory access patterns in kernel space originating from WLAN driver components
• Unauthorized privilege transitions from user-level processes accessing wireless interfaces
• System logs indicating driver faults or memory violations in MediaTek wireless modules

Detection Strategies

• Deploy endpoint detection and response (EDR) solutions capable of monitoring kernel driver behavior and detecting anomalous memory operations
• Implement kernel integrity monitoring to detect unauthorized modifications to kernel memory structures
• Monitor for unusual process privilege escalations, particularly those correlated with wireless interface activity
• Enable driver verification and code signing enforcement to detect tampered or malicious driver binaries

Monitoring Recommendations

• Configure kernel auditing to log all interactions with wireless driver interfaces
• Implement network-based monitoring for devices using affected MediaTek chipsets to identify potential compromise indicators
• Establish baseline behavior for WLAN driver operations and alert on deviations
• Deploy file integrity monitoring on driver binary files to detect unauthorized modifications

How to Mitigate CVE-2026-20407

Immediate Actions Required

• Apply the security patch released by MediaTek as documented in the MediaTek Security Bulletin - February 2026
• Inventory all systems using affected MediaTek wireless chipsets (MT7902, MT7920, MT7921, MT7922, MT7925, MT7927) or NB-IoT SDK
• Prioritize patching for systems in high-risk environments or those accessible to untrusted users
• Implement additional access controls to limit local user access on affected systems until patches are applied

Patch Information

MediaTek has released a security patch addressing this vulnerability. The patch implements proper bounds checking in the WLAN STA driver to prevent out-of-bounds write conditions. The fix is identified by Patch ID WCNCR00464377 and addresses Issue ID MSV-4905.

Organizations should obtain the patched driver through their device manufacturers or OEM partners who integrate MediaTek wireless chipsets. For systems using the NB-IoT SDK, update to the latest SDK version that includes this security fix.

Refer to the MediaTek Security Bulletin - February 2026 for detailed patch information and affected version specifics.

Workarounds

• Restrict local user access on systems with affected MediaTek wireless chipsets to trusted administrators only
• Implement application whitelisting to prevent unauthorized processes from interacting with wireless driver interfaces
• Deploy mandatory access control (MAC) policies such as SELinux or AppArmor to constrain driver interactions
• Consider disabling wireless functionality on critical systems if not operationally required until patches are applied