CVE-2026-20478 Overview
CVE-2026-20478 is an out-of-bounds write vulnerability in the MediaTek Audio Hardware Abstraction Layer (HAL). The flaw stems from a heap buffer overflow that a local attacker with user execution privileges can trigger without user interaction. Successful exploitation leads to a local denial of service (DoS) condition on affected MediaTek chipsets. MediaTek addressed the issue in patch ALPS10981454 for MT6880, MT6890, MT6988, and MT6990, and in patch AUTO00851293 for MT2735 and MT2737. The issue is tracked internally by MediaTek as MSV-7638 and is categorized under CWE-787: Out-of-bounds Write.
Critical Impact
A local attacker with low privileges can trigger a heap buffer overflow in the Audio HAL, causing a denial of service on the affected MediaTek chipset without any user interaction.
Affected Products
- MediaTek chipsets MT6880, MT6890, MT6988, and MT6990 (patch ALPS10981454)
- MediaTek automotive chipsets MT2735 and MT2737 (patch AUTO00851293)
- Devices integrating the affected MediaTek Audio HAL component
Discovery Timeline
- 2026-08-03 - CVE-2026-20478 published to NVD
- 2026-08-03 - Last updated in NVD database
- August 2026 - MediaTek published the issue in the MediaTek Security Bulletin August 2026
Technical Details for CVE-2026-20478
Vulnerability Analysis
The vulnerability resides in the MediaTek Audio HAL, a userspace component that mediates between the Android audio framework and the underlying audio hardware. The Audio HAL processes audio buffers and control structures on behalf of privileged audio services. A heap buffer overflow in this component allows an out-of-bounds write beyond an allocated heap region. Because the Audio HAL runs within a process that handles audio I/O, corrupting adjacent heap metadata or object fields destabilizes the process and terminates audio-related services.
The attack requires only local access with low privileges and no user interaction. The impact is limited to availability, with no confidentiality or integrity consequences reported by MediaTek.
Root Cause
The root cause is missing or insufficient bounds validation on data written into a heap-allocated buffer inside the Audio HAL. When the size of input data exceeds the expected buffer length, the write operation crosses the allocation boundary and corrupts adjacent heap memory. This class of defect is classified as [CWE-787: Out-of-bounds Write].
Attack Vector
An attacker executing code on the device as an unprivileged local user issues crafted requests to the Audio HAL through the exposed audio interfaces. The malformed input triggers the vulnerable write path inside the HAL, corrupting heap memory and causing the audio process to crash. Repeated exploitation produces a persistent denial of service against audio functionality on the device. Remote exploitation is not possible; the attacker must already have code execution on the target.
No public proof-of-concept code has been released for CVE-2026-20478. See the MediaTek Security Bulletin August 2026 for vendor technical details.
Detection Methods for CVE-2026-20478
Indicators of Compromise
- Unexpected crashes or restarts of the Android audio server (audioserver) or MediaTek Audio HAL process on affected chipsets
- Kernel or tombstone logs referencing SIGSEGV or SIGABRT within Audio HAL libraries
- Presence of unpatched builds lacking patch IDs ALPS10981454 or AUTO00851293 on affected MediaTek platforms
Detection Strategies
- Inventory devices by chipset and firmware level to identify systems running vulnerable MediaTek Audio HAL builds
- Monitor Android logcat, dmesg, and tombstone output for repeated Audio HAL process aborts that correlate with heap corruption signatures
- Correlate low-privileged process activity that interacts with audio interfaces against subsequent Audio HAL crashes to identify exploitation attempts
Monitoring Recommendations
- Forward mobile telemetry, crash reports, and MDM inventory data into a centralized analytics platform for baseline and anomaly detection
- Alert on unpatched MediaTek firmware builds surfaced by mobile device management or fleet inventory tools
- Track vendor security bulletins and map new patch IDs against enrolled device inventories monthly
How to Mitigate CVE-2026-20478
Immediate Actions Required
- Apply the MediaTek patches ALPS10981454 (MT6880, MT6890, MT6988, MT6990) and AUTO00851293 (MT2735, MT2737) through the device vendor's firmware update process
- Restrict installation of untrusted third-party applications on affected devices to reduce the pool of local attackers
- Enroll affected devices in mobile device management to enforce OS and firmware update policies
Patch Information
MediaTek documented the fix in the MediaTek Security Bulletin August 2026 under Issue ID MSV-7638. Device manufacturers must integrate the referenced patch IDs into their firmware releases and distribute them to end users as an over-the-air update.
Workarounds
- No official workaround has been published by MediaTek; applying the vendor patch is the supported remediation
- Limit application sideloading and enforce app store vetting to reduce exposure to malicious local code
- For automotive deployments using MT2735 or MT2737, coordinate with the OEM to schedule firmware updates containing patch AUTO00851293
# Verify MediaTek patch level on an Android device via adb
adb shell getprop ro.build.version.security_patch
adb shell getprop ro.vendor.mediatek.platform
adb shell getprop ro.build.fingerprint
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
