CVE-2023-20694 Overview
CVE-2023-20694 is an out-of-bounds write vulnerability [CWE-787] in the MediaTek preloader component affecting a broad range of MediaTek chipsets used in Android devices and OpenWrt-based systems. The flaw stems from a missing bounds check, allowing a local attacker with high privileges to write outside intended memory boundaries. Successful exploitation leads to local escalation of privilege with System execution privileges. User interaction is not required. MediaTek tracks the issue under Patch IDs ALPS07733998 and ALPS07874388 (the latter applying to MT6880 and MT6890 only).
Critical Impact
Local privilege escalation to System-level execution on dozens of MediaTek chipsets used in Android smartphones, tablets, and embedded devices.
Affected Products
- Google Android 12.0 and 13.0 running on affected MediaTek chipsets
- OpenWrt 19.07.0 and 21.02.0 on affected MediaTek platforms
- MediaTek chipsets including MT6580, MT6739, MT6761, MT6765, MT6768, MT6769, MT6771, MT6779, MT6785, MT6789, MT6853, MT6855, MT6873, MT6879, MT6880, MT6885, MT6890, MT6895, MT6983, MT8167, MT8175, MT8185, MT8195, MT8321, MT8365, MT8385, MT8395, MT8666, MT8667, MT8673, MT8675, MT8765, MT8766, MT8768, MT8781, MT8786, MT8788, MT8789, MT8791, MT8791T, and MT8797
Discovery Timeline
- 2023-05-15 - CVE-2023-20694 published to the National Vulnerability Database (NVD)
- 2023-05 - MediaTek publishes the MediaTek Security Bulletin May 2023 with fixes
- 2025-01-23 - Record last modified in NVD
Technical Details for CVE-2023-20694
Vulnerability Analysis
The vulnerability resides in the MediaTek preloader, a low-level bootloader component that runs before the main Android boot chain. The preloader initializes hardware, validates and loads subsequent boot stages, and handles initial memory configuration. Because it executes in a highly privileged context with direct hardware access, defects in this component can undermine every layer of the operating system that loads afterwards.
The flaw is an out-of-bounds write caused by a missing bounds check on data processed by the preloader. An attacker with local access and high privileges can supply input that drives the preloader to write past the end of an intended buffer, corrupting adjacent memory used by the boot environment.
Successful exploitation results in escalation of privilege to System execution privileges. The attack requires no user interaction and impacts confidentiality, integrity, and availability of the device.
Root Cause
The root cause is the absence of a length or index validation step prior to a write operation in the preloader. Without the bounds check, attacker-controlled size or offset values are trusted, allowing the write to extend beyond the destination buffer. This pattern is classified under [CWE-787: Out-of-bounds Write].
Attack Vector
The attack vector is local. An attacker must already possess high privileges on the device to deliver crafted input to the preloader's vulnerable code path. From that position the attacker can corrupt preloader memory and pivot to executing code with System-level privileges, defeating Android's privilege separation model.
No public proof-of-concept code or exploit details have been released, and the issue is not listed in the CISA Known Exploited Vulnerabilities catalog. The vulnerability is described in prose in the MediaTek advisory; no verified exploitation code is available.
Detection Methods for CVE-2023-20694
Indicators of Compromise
- Unexpected bootloader or preloader crashes, reboot loops, or boot-time error messages on affected MediaTek devices
- Unauthorized modifications to boot partitions, preloader images, or firmware-resident configuration
- Presence of System-privileged processes or binaries that were not deployed through approved channels
Detection Strategies
- Validate device firmware versions against the patched builds listed in the MediaTek Security Bulletin for May 2023 and corresponding OEM Android security patch levels
- Inspect Android Verified Boot (AVB) and dm-verity state to identify devices where boot integrity has been disabled or tampered with
- Use mobile device management (MDM) attestation, including Android KeyAttestation and Play Integrity verdicts, to identify devices reporting failed integrity or outdated patch levels
Monitoring Recommendations
- Continuously inventory mobile and embedded devices by chipset and Android security patch level to surface unpatched MediaTek hardware
- Alert on devices that fail boot attestation or report bootloader unlock state in enterprise fleets
- Correlate privilege escalation indicators on Android endpoints with firmware-level telemetry where available
How to Mitigate CVE-2023-20694
Immediate Actions Required
- Apply the OEM firmware update that incorporates MediaTek Patch IDs ALPS07733998 and, for MT6880 and MT6890 devices, ALPS07874388
- Update affected Android devices to the security patch level that addresses the May 2023 MediaTek bulletin
- Restrict physical access and limit which accounts and applications can obtain elevated privileges on affected devices
- Enforce bootloader lock state and full-disk encryption on managed Android endpoints
Patch Information
MediaTek released fixes under Patch ID ALPS07733998 for the general set of affected chipsets and Patch ID ALPS07874388 specifically for MT6880 and MT6890. Patches are delivered to end users through device OEM firmware updates and the monthly Android security update channel. Refer to the MediaTek Security Bulletin May 2023 for the authoritative list of affected chipsets and remediation guidance.
Workarounds
- No vendor-supplied workaround exists; firmware updates from the device OEM are the only complete remediation
- Reduce exposure by removing or sandboxing untrusted applications that could be leveraged to gain the high privileges required for exploitation
- Decommission or isolate end-of-life MediaTek devices that will not receive vendor firmware updates
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
