CVE-2026-20466 Overview
CVE-2026-20466 is a heap buffer overflow vulnerability in the MediaTek secure boot (sec boot) component. The flaw allows a local attacker with physical access to escalate privileges on affected devices without user interaction or additional execution privileges. MediaTek tracks the issue as MSV-6929 and has issued patches under IDs AUTO00845351 (for MT2737) and ALPS11072643 (for MT6880, MT6890, and MT6990). The weakness is categorized under [CWE-787] (Out-of-bounds Write). Because the flaw resides in the secure boot chain, successful exploitation undermines a foundational trust component of the boot process.
Critical Impact
An attacker with physical access can trigger a heap buffer overflow in the secure boot path to gain elevated privileges, compromising the device's chain of trust.
Affected Products
- MediaTek MT2737 automotive chipset
- MediaTek MT6880 modem platform
- MediaTek MT6890 and MT6990 platforms
Discovery Timeline
- 2026-08-03 - CVE-2026-20466 published to NVD
- 2026-08-03 - MediaTek Security Bulletin August 2026 released
- 2026-08-03 - Last updated in NVD database
Technical Details for CVE-2026-20466
Vulnerability Analysis
The vulnerability resides in the sec boot component used across several MediaTek chipset families. During boot processing, the component writes data to a heap-allocated buffer without adequately validating the length or boundaries of the input. This produces an out-of-bounds write on the heap ([CWE-787]).
Because secure boot runs before the operating system, corruption at this stage can influence subsequent boot stages and the integrity of the trusted execution environment. Confidentiality and integrity impacts are high, while availability is not affected according to the published CVSS vector. The MediaTek Security Bulletin for August 2026 references the flaw under MSV-6929.
Root Cause
The root cause is missing or incorrect bounds enforcement when the secure boot routine copies attacker-influenced data into a heap buffer. The routine trusts a length or offset value that an attacker can manipulate through physical interfaces, causing the write to extend beyond the allocated region and corrupt adjacent heap metadata or control data.
Attack Vector
The CVSS vector AV:P indicates the attacker requires physical access to the device. No privileges and no user interaction are required. An attacker in possession of the device can supply crafted boot inputs, such as through debug interfaces, external storage, or crafted boot images consumed by sec boot, to trigger the overflow and execute code with elevated privileges. No verified public exploit code is available for this issue.
See the MediaTek Security Bulletin August 2026 for vendor technical details.
Detection Methods for CVE-2026-20466
Indicators of Compromise
- Unexpected boot failures, boot loops, or secure boot verification errors on affected MediaTek platforms.
- Firmware version strings that do not include patch identifiers AUTO00845351 (MT2737) or ALPS11072643 (MT6880, MT6890, MT6990).
- Evidence of physical tampering, unauthorized JTAG or USB debug connections, or unexpected external boot media.
Detection Strategies
- Inventory MediaTek-based devices and correlate firmware build identifiers against the fixed patch IDs published in the MediaTek bulletin.
- Audit device provisioning and repair workflows for gaps that could permit attacker physical access to boot interfaces.
- Where platforms expose secure boot measurement logs or attestation data, verify boot measurements against known-good baselines.
Monitoring Recommendations
- Monitor fleet management and MDM telemetry for firmware versions that lag behind the August 2026 MediaTek patch level.
- Track device custody events and physical access to production, staging, and returned hardware.
- Alert on repeated boot verification failures reported by device diagnostics.
How to Mitigate CVE-2026-20466
Immediate Actions Required
- Apply the MediaTek-supplied firmware update containing patch AUTO00845351 for MT2737 and ALPS11072643 for MT6880, MT6890, and MT6990 as soon as the OEM makes it available.
- Coordinate with device OEMs and carriers to confirm distribution timelines for downstream firmware images.
- Restrict physical access to sensitive or high-value devices until patches are deployed.
Patch Information
MediaTek published fixes in the MediaTek Security Bulletin August 2026. The vendor lists patch AUTO00845351 for MT2737 and ALPS11072643 for MT6880, MT6890, and MT6990, tracked as issue MSV-6929. Device manufacturers must integrate the patch into their firmware builds and ship updates to end users.
Workarounds
- Enforce strict physical security controls for affected devices, particularly in automotive and telecom deployments.
- Disable or lock down external debug interfaces, USB boot paths, and removable boot media where the platform permits.
- Use tamper-evident seals and custody logging for devices that leave controlled environments for service or repair.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
