CVE-2026-20472: TFA Out of Bounds Write DoS Vulnerability

CVE-2026-20472 Overview

CVE-2026-20472 is an out-of-bounds write vulnerability in MediaTek's Trusted Firmware-A (TFA) component. The flaw stems from a missing bounds check that permits memory to be written outside its intended region. Exploitation requires local access and pre-existing System privileges, limiting the practical attack surface. Successful exploitation can trigger a local denial of service condition on affected MediaTek devices.

MediaTek tracks the fix under Patch ID ALPS10991467 and internal Issue ID MSV-7764. The vulnerability is classified under CWE-787 (Out-of-bounds Write).

Critical Impact
A local attacker with System privileges can trigger an out-of-bounds write in TFA, resulting in denial of service without user interaction.

Affected Products

MediaTek Trusted Firmware-A (TFA) component
Devices incorporating vulnerable MediaTek chipsets — refer to the MediaTek Product Security Bulletin for the authoritative product list
Downstream OEM builds that ship the unpatched TFA image

Discovery Timeline

2026-08-03 - CVE-2026-20472 published to NVD
2026-08-03 - Last updated in NVD database

Technical Details for CVE-2026-20472

Vulnerability Analysis

The vulnerability resides in MediaTek's Trusted Firmware-A (TFA), the reference secure-world firmware implementation used on ARM-based mobile platforms. TFA runs at Exception Level 3 (EL3) and mediates secure monitor calls between the non-secure world and secure services. A missing bounds check in a TFA code path allows writing beyond the boundaries of an intended buffer.

Because the write is unchecked, an attacker in control of the input can corrupt adjacent memory within the secure firmware's address space. The resulting corruption produces unpredictable state, most commonly leading to a crash of the secure monitor and denial of service on the device.

Exploitation requires attacker code to already be running with System privilege. This precondition means the flaw is not directly reachable from unprivileged applications or over the network.

Root Cause

The root cause is the absence of a boundary validation check before performing a memory write operation within TFA. When attacker-supplied length or index values reach the vulnerable code path, the write extends past the destination buffer. This matches the classic CWE-787 pattern where trusted code fails to validate size or offset parameters prior to a copy or store operation.

Attack Vector

The attack vector is local. A process running with System privilege on the target device invokes the vulnerable TFA interface with crafted parameters. No user interaction is required. The impact is limited to availability — the vulnerability does not directly disclose data or enable code execution according to the assigned CVSS metrics. Technical specifics of the vulnerable interface are not published; refer to the MediaTek Product Security Bulletin for vendor-authoritative detail.

Detection Methods for CVE-2026-20472

Indicators of Compromise

Unexpected secure monitor crashes or panics referencing TFA/BL31 in device logs
Repeated device reboots or watchdog-triggered resets originating from EL3
Kernel logs showing failed or malformed secure monitor calls (smc traps) from System-privileged processes

Detection Strategies

Collect and centrally analyze dmesg, logcat, and vendor bootloader logs for TFA panic signatures
Baseline the frequency of secure monitor call failures per device; alert on statistically significant spikes
Correlate device instability with recently installed or updated System-privileged applications and services

Monitoring Recommendations

Ingest mobile device management (MDM) telemetry into the security data lake to identify fleet-wide crash patterns
Track MediaTek patch level compliance across managed endpoints and flag devices missing the August 2026 bulletin fixes
Monitor for privilege escalation activity that could position an attacker to reach System context on MediaTek devices

How to Mitigate CVE-2026-20472

Immediate Actions Required

Apply the MediaTek firmware update containing Patch ID ALPS10991467 as delivered by the device OEM
Inventory MediaTek-based devices in your fleet and prioritize patch deployment to devices exposed to untrusted System-privileged code paths
Restrict installation of applications and services that require or can obtain System-level privileges

Patch Information

MediaTek has released a fix identified as Patch ID ALPS10991467 (Issue ID MSV-7764). The patch is distributed to device manufacturers and delivered to end users through OEM firmware updates. Consult the MediaTek Product Security Bulletin (August 2026) for the definitive advisory and the list of affected chipsets.

Workarounds

No vendor-supplied workaround is published; firmware update from the OEM is the authoritative remediation
Reduce risk by enforcing least-privilege on device management agents and removing unnecessary System-privileged software
Enroll devices in MDM policies that block sideloading and enforce timely firmware update installation

bash

# Verify MediaTek security patch level on an Android device via adb
adb shell getprop ro.build.version.security_patch
adb shell getprop ro.vendor.build.security_patch

# Confirm the device is on the August 2026 (or later) MediaTek patch level
# Expected: 2026-08-01 or later