CVE-2026-20493: WiFi Out of Bounds Write DoS Vulnerability

CVE-2026-20493 Overview

CVE-2026-20493 is an out-of-bounds write vulnerability in the MediaTek Wi-Fi component caused by a missing bounds check [CWE-787]. An attacker with existing System privilege can trigger the flaw to cause a local denial of service on affected devices. No user interaction is required for exploitation. MediaTek tracks the fix under Patch ID BORA00154903 and Issue ID MSV-7575, published in the MediaTek Security Bulletin for August 2026.

Critical Impact
Local denial of service on MediaTek-based devices, exploitable by a threat actor that has already achieved System-level privilege on the target.

Affected Products

MediaTek Wi-Fi component (specific chipset models listed in the MediaTek August 2026 Security Bulletin)
Android devices integrating the affected MediaTek Wi-Fi firmware/driver
Patch reference: BORA00154903 / Issue ID MSV-7575

Discovery Timeline

2026-08-03 - CVE-2026-20493 published to NVD
2026-08-03 - Last updated in NVD database
August 2026 - Fix released in the MediaTek Security Bulletin August 2026

Technical Details for CVE-2026-20493

Vulnerability Analysis

The flaw sits in the MediaTek Wi-Fi driver code path where an input length or index is used to write into a buffer without validating the value against the destination size. Because bounds validation is absent, a crafted parameter causes the driver to write past the allocated buffer. The resulting memory corruption destabilizes the kernel or driver state and leads to a denial-of-service condition on the device.

The attack surface is local. The CVSS vector indicates the attacker must already hold high privileges on the device, and the impact is limited to availability. Confidentiality and integrity are not directly affected, but the write primitive within a privileged component can be used to disrupt Wi-Fi functionality and force device or subsystem restarts.

Root Cause

The root cause is a missing bounds check before a memory write operation in the MediaTek Wi-Fi driver, categorized under [CWE-787] Out-of-Bounds Write. Untrusted or attacker-controlled length/offset values reach a write routine without verification against the target buffer's allocated size.

Attack Vector

Exploitation requires local access with System privilege already established. An attacker that has compromised a System-level process invokes the affected Wi-Fi driver interface with crafted parameters. The driver performs the write beyond the intended bounds, corrupting adjacent memory and triggering a crash or hang. Because user interaction is not required, this vulnerability is well-suited to post-exploitation chains where the attacker seeks to disable Wi-Fi, disrupt device functionality, or destabilize the platform.

No public proof-of-concept code is available. Refer to the MediaTek Security Bulletin August 2026 for vendor technical details.

Detection Methods for CVE-2026-20493

Indicators of Compromise

Repeated kernel oops or panic entries referencing the MediaTek Wi-Fi driver in dmesg or Android bug reports
Unexpected Wi-Fi service restarts or wlan0 interface flapping without a corresponding user action
Presence of System-level processes making anomalous ioctl calls to the Wi-Fi driver

Detection Strategies

Monitor Android device logs and vendor telemetry for driver crash signatures tied to the MediaTek Wi-Fi module
Correlate System-privilege process anomalies with Wi-Fi subsystem failures to identify post-exploitation activity
Track device firmware/patch level against the MediaTek August 2026 Security Bulletin to identify unpatched fleet members

Monitoring Recommendations

Ingest mobile device management (MDM) and endpoint telemetry into a centralized data lake for correlation of crash events across devices
Alert on repeated Wi-Fi driver faults on the same device within short time windows
Track patch-level compliance for all MediaTek-based mobile assets in the enterprise

How to Mitigate CVE-2026-20493

Immediate Actions Required

Apply the OEM security update that incorporates MediaTek Patch ID BORA00154903 as soon as it is available for your device model
Inventory MediaTek-based mobile devices and identify those running firmware predating the August 2026 security patch level
Enforce mobile OS patch-level policies through MDM to block or restrict non-compliant devices

Patch Information

MediaTek addressed the issue under Patch ID BORA00154903 (Issue ID MSV-7575) in the MediaTek Security Bulletin August 2026. Device OEMs must integrate the MediaTek fix into their monthly security patch level (SPL) for downstream distribution. Users should install the August 2026 or later security patch level from their device manufacturer.

Workarounds

No vendor-supplied workaround is published; patching is the supported remediation
Reduce residual risk by hardening the device against local privilege escalation, since exploitation requires prior System privilege
Restrict installation of untrusted applications and enforce Verified Boot to limit paths to System-level compromise

bash

# Verify Android security patch level on a connected device
adb shell getprop ro.build.version.security_patch

# Confirm the patch level is 2026-08-01 or later before returning the device to service