CVE-2024-23923: Alpine Halo9 Use-After-Free RCE Flaw

CVE-2024-23923 Overview

CVE-2024-23923 is a use-after-free vulnerability [CWE-416] in the Alpine Halo9 in-vehicle infotainment platform. The flaw resides in the prh_l2_sar_data_ind function and allows network-adjacent attackers to execute arbitrary code on affected ILX-F509 devices. Exploitation does not require authentication. Successful exploitation grants code execution in the context of root, giving an attacker full control of the head unit.

The issue was originally tracked as ZDI-CAN-22945 and disclosed through the Zero Day Initiative as advisory ZDI-24-844.

Critical Impact
An unauthenticated adjacent-network attacker can achieve remote code execution as root on Alpine Halo9 ILX-F509 head units, compromising the vehicle infotainment system.

Affected Products

Alps Alpine ILX-F509 (hardware)
Alps Alpine ILX-F509 firmware version 6.0.000
Alpine Halo9 in-vehicle infotainment platform

Discovery Timeline

2024-09-28 - CVE-2024-23923 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-23923

Vulnerability Analysis

The vulnerability is a use-after-free condition [CWE-416] inside the prh_l2_sar_data_ind function of the Alpine Halo9 firmware. This function processes segmentation and reassembly (SAR) data indications at layer 2 of the device's packet reassembly subsystem. When invoked, the function operates on an object without first validating that the object still exists in memory. An attacker who can send crafted messages to the affected interface triggers reuse of a freed object. Corrupting the freed allocation allows the attacker to hijack control flow and execute arbitrary code as root.

Because the attack vector is adjacent network, the attacker must be on the same logical network segment as the head unit. This includes wireless interfaces exposed by the infotainment system such as paired Bluetooth or Wi-Fi links.

Root Cause

The root cause is missing object lifetime validation in prh_l2_sar_data_ind. The function dereferences a pointer to a data structure that may have already been released by another code path. Without a null check or reference-count validation before use, the freed memory is accessed and can be reallocated by attacker-controlled data.

Attack Vector

An attacker within adjacent network range sends specially crafted SAR data indication frames to the Halo9 device. The malformed sequence forces the driver to free an object while a stale reference remains in use. The attacker then reclaims the freed allocation with controlled data and triggers subsequent operations that dereference the poisoned pointer, achieving code execution as root.

No verified public proof-of-concept code is available. Technical details are documented in the Zero Day Initiative Advisory ZDI-24-844.

Detection Methods for CVE-2024-23923

Indicators of Compromise

Unexpected reboots, crashes, or watchdog resets of the Alpine Halo9 head unit
Anomalous outbound network connections originating from the infotainment unit
Unrecognized processes or modified system binaries observed during firmware forensics
Unusual Bluetooth or Wi-Fi pairing activity preceding device instability

Detection Strategies

Monitor CAN bus and in-vehicle Ethernet traffic for malformed SAR/L2 packet sequences targeting the head unit
Baseline expected traffic patterns from the infotainment unit and alert on deviations such as new outbound destinations
Compare firmware image hashes against known-good vendor images to identify tampering

Monitoring Recommendations

Enable logging on any gateway or telematics control unit that mediates traffic to the Halo9 device
Track pairing and connection events on Bluetooth and Wi-Fi radios exposed by the head unit
Review vendor security bulletins from Alps Alpine and Zero Day Initiative advisories for related IVI vulnerabilities

How to Mitigate CVE-2024-23923

Immediate Actions Required

Contact Alps Alpine or an authorized dealer to obtain the latest firmware update for the ILX-F509
Inventory fleet vehicles equipped with affected Halo9 head units and prioritize firmware remediation
Disable or restrict adjacent-network interfaces such as Wi-Fi hotspot mode when not required
Limit Bluetooth pairing to trusted devices and remove unknown paired endpoints

Patch Information

Refer to the Zero Day Initiative Advisory ZDI-24-844 for vendor coordination status. Owners and fleet operators should consult Alps Alpine directly for firmware releases addressing ILX-F509 firmware version 6.0.000. No vendor advisory URL is listed in the NVD record at the time of publication.

Workarounds

Turn off Wi-Fi and Bluetooth radios on the head unit when not actively in use
Avoid connecting the infotainment system to untrusted wireless networks or unknown mobile hotspots
Segment in-vehicle networks so the head unit cannot be reached from external telematics interfaces where feasible

bash

# Configuration example: recommended user-facing hardening steps on the head unit
# 1. Open Settings > Bluetooth and remove untrusted paired devices
# 2. Open Settings > Wi-Fi and disable auto-connect to open networks
# 3. Disable Wi-Fi hotspot / tethering features when unused
# 4. Apply the latest Alps Alpine firmware update via authorized service center