CVE-2025-34251: Tesla TCU Auth Bypass Vulnerability

CVE-2025-34251 Overview

CVE-2025-34251 is an authentication bypass vulnerability in Tesla Telematics Control Unit (TCU) firmware prior to version v2025.14. The TCU runs the Android Debug Bridge daemon (adbd) as root. A lockdown check disables adb shell, but adb push, adb pull, and adb forward remain available. An attacker with physical access to the externally exposed USB port can write arbitrary files and overwrite kernel hotplug handlers, achieving root code execution. The flaw is categorized under [CWE-269] Improper Privilege Management.

Critical Impact
An attacker with physical USB access to the TCU can gain root code execution on the Tesla telematics subsystem, compromising vehicle confidentiality, integrity, and availability.

Affected Products

Tesla Telematics Control Unit (TCU) firmware prior to v2025.14
Tesla vehicles shipping with the affected TCU hardware revision
Android Debug Bridge daemon (adbd) running on the TCU as root

Discovery Timeline

2025-10-07 - CVE-2025-34251 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-34251

Vulnerability Analysis

The Tesla TCU ships with adbd running as the root user. Tesla implemented a lockdown mode intended to restrict ADB access, but the restriction only blocks the interactive adb shell command. Filesystem and forwarding subcommands remain reachable through the same authenticated channel. Because the daemon executes with root privileges, any file written via adb push inherits the daemon's privilege context for subsequent operations.

An attacker plugs into the externally accessible USB port and writes a shell script to a writable filesystem location. The attacker then overwrites either the kernel uevent_helper path or the /proc/sys/kernel/hotplug entry to reference that script. When the kernel triggers a hotplug event, it executes the attacker-controlled script as root, completing the privilege escalation chain.

Root Cause

The root cause is incomplete enforcement of the ADB lockdown policy combined with running adbd as root. The lockdown logic gates only the shell subcommand and leaves file transfer and port forwarding primitives unguarded, violating least privilege expectations expressed by [CWE-269].

Attack Vector

Exploitation requires physical access to the vehicle's USB port connected to the TCU. No authentication, user interaction, or remote network connectivity is required once physical access is established. The attacker uses standard adb client tooling to deliver the payload and trigger the kernel hotplug execution path. Verified code examples are not publicly available; see the NCC Group Technical Advisory and the VulnCheck Advisory on Tesla TCU for the full technical write-up.

Detection Methods for CVE-2025-34251

Indicators of Compromise

Unexpected modifications to /proc/sys/kernel/hotplug or the kernel uevent_helper setting on the TCU
Presence of unknown executable scripts in TCU writable directories such as /data/ or /tmp/
USB connection events on the TCU port outside of authorized service workflows
adbd child processes spawning non-standard binaries with uid=0

Detection Strategies

Monitor TCU firmware version reporting and alert when units run firmware older than v2025.14
Audit ADB connection logs for push, pull, and forward activity originating from non-service USB hosts
Validate the integrity of kernel hotplug configuration values against a known-good baseline at boot

Monitoring Recommendations

Track physical USB access events to vehicle service ports in fleet telemetry where supported
Centralize TCU logs and watch for adbd-initiated filesystem writes outside of update windows
Correlate hotplug-triggered process executions with recent USB attach events to identify exploitation attempts

How to Mitigate CVE-2025-34251

Immediate Actions Required

Update affected Tesla TCU firmware to version v2025.14 or later through the official Tesla over-the-air update channel
Inventory vehicles by TCU firmware version and prioritize updates for units in shared, fleet, or rental deployments
Restrict physical access to the vehicle's diagnostic USB port, especially in service and storage environments

Patch Information

Tesla addressed CVE-2025-34251 in TCU firmware v2025.14. The fix tightens the ADB lockdown enforcement so that file transfer and forwarding subcommands are blocked alongside adb shell when the device is in lockdown state. Refer to the Tesla Official Website for vehicle-specific update guidance and confirm the deployed firmware version after the update completes.

Workarounds

Physically restrict or disable access to the externally exposed USB port until firmware v2025.14 is installed
Implement custody controls and tamper-evident seals on service ports for high-value or fleet vehicles
Limit vehicle service operations to authorized technicians using monitored host systems

The vulnerability requires physical access and is firmware-specific to the Tesla TCU; no host-based endpoint configuration applies. See the linked vendor and third-party advisories for additional remediation guidance.