CVE-2024-6287

Executive Summary

CVE-2024-6287 is a high-severity vulnerability in Renesas arm-trusted-firmware (ATF) that allows local code execution due to an incorrect calculation when checking memory overlap during image loading. The flaw enables an attacker to bypass memory range restrictions and overwrite previously loaded images, potentially compromising secure boot and executing arbitrary code. With a CVSS score of 7.5, this vulnerability poses a significant risk to devices using Renesas ATF, particularly in embedded and IoT environments where secure boot is critical.

Supply Chain & Package Security

This vulnerability affects the Renesas arm-trusted-firmware, which is a critical component in the secure boot chain for Renesas-based systems. The firmware is typically distributed as part of board support packages (BSPs) or firmware updates. Organizations should verify the integrity of their firmware supply chain and ensure that only trusted sources are used for updates.

CVSS Breakdown & Threat Level

• CVSS Score: 7.5 (High)
• Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Local (AV:L) – Requires physical or local access to the device.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Unchanged (S:U) – Vulnerability does not affect other components.
• Confidentiality Impact: High (C:H) – Potential for full data disclosure.
• Integrity Impact: High (I:H) – Potential for arbitrary code execution.
• Availability Impact: High (A:H) – Potential for system compromise.

Threat Level: High. The vulnerability allows local attackers to bypass secure boot and execute arbitrary code, which could lead to complete device compromise.

Deep Dive & Mechanics

The vulnerability resides in the memory overlap checking logic within Renesas arm-trusted-firmware. When loading a new image, the firmware checks whether the new image overlaps with any previously loaded images. However, the calculation neglects to consider certain edge cases, such as:

• Partial overlap at the start or end of a region
• Images that are completely contained within another image
• Images that span multiple memory regions

This oversight allows an attacker to craft a malicious image that bypasses the overlap check, enabling them to overwrite a previously loaded image (e.g., the bootloader or secure monitor). By overwriting critical firmware components, the attacker can execute arbitrary code with elevated privileges, effectively bypassing secure boot.

The attack requires local access to the device (e.g., via a compromised peripheral or physical access) and the ability to load a malicious image during the boot process.

Vulnerable vs. Patched Code

The vulnerable code likely resides in the image loading function, where memory overlap is checked. A simplified example of the vulnerable logic:

// Vulnerable code
bool check_overlap(uintptr_t new_start, size_t new_size, uintptr_t old_start, size_t old_size) {
    uintptr_t new_end = new_start + new_size;
    uintptr_t old_end = old_start + old_size;
    // Incorrect: only checks if new_start is within old region
    if (new_start >= old_start && new_start < old_end) {
        return true; // overlap detected
    }
    return false;
}

The patched code should consider all overlap scenarios:

// Patched code
bool check_overlap(uintptr_t new_start, size_t new_size, uintptr_t old_start, size_t old_size) {
    uintptr_t new_end = new_start + new_size;
    uintptr_t old_end = old_start + old_size;
    // Correct: checks if regions overlap
    if (new_start < old_end && new_end > old_start) {
        return true; // overlap detected
    }
    return false;
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Physical or local access to a device running vulnerable Renesas ATF.
• Ability to load a custom firmware image during boot (e.g., via JTAG, UART, or compromised boot media).

Exploitation Steps:

1. Identify the memory layout of the target device (e.g., via datasheet or reverse engineering).
2. Craft a malicious firmware image that overlaps with a critical region (e.g., the bootloader or secure monitor).
3. Load the malicious image during the boot process (e.g., via a compromised update mechanism or direct memory write).
4. The vulnerable overlap check fails to detect the overlap, allowing the malicious image to overwrite the target region.
5. The overwritten code executes, granting arbitrary code execution with elevated privileges.

Example payload (pseudo-code):

# Craft a malicious image that overlaps with the bootloader
malicious_image = b"\x00" * 0x1000  # Placeholder for shellcode
# Overlap with bootloader region (e.g., 0x1000-0x2000)
load_image(malicious_image, base_address=0x0F00, size=0x1200)

Blue Team

Detection:

• Monitor for unexpected firmware loading events.
• Implement integrity checks for all loaded images (e.g., cryptographic hashes).
• Use hardware security modules (HSMs) to verify image signatures.

Mitigation:

• Apply patches from Renesas as soon as available.
• Restrict physical access to devices.
• Enable secure boot with verified boot chains.
• Use memory protection units (MPUs) to enforce memory region permissions.

Indicators of Compromise (IOCs)

• File Hashes: (None available publicly)
• Network Signatures: (None – local attack)
• Behavioral Indicators:
  • Unexpected firmware loading events in system logs.
  • Modification of secure boot variables.
  • Execution of unsigned code during boot.
• Memory Artifacts:
  • Overwritten bootloader or secure monitor regions.
  • Anomalous memory mappings.

Detection Engineering

YARA Rule

rule CVE_2024_6287_Renesas_ATF_Overlap {
    meta:
        description = "Detects potential exploitation of CVE-2024-6287 in Renesas ATF"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-6287"
    strings:
        $overlap_check = { 48 8B 45 ?? 48 03 45 ?? 48 39 45 ?? 0F 82 ?? ?? ?? ?? }  // vulnerable overlap check pattern
        $malicious_image = "Renesas"  // placeholder for malicious image marker
    condition:
        $overlap_check or $malicious_image
}

Sigma Rule

title: CVE-2024-6287 - Renesas ATF Memory Overlap Exploitation
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects attempts to exploit memory overlap vulnerability in Renesas ATF
author: Valters IT
date: 2025-04-10
logsource:
    product: linux
    service: syslog
detection:
    selection:
        - "Renesas ATF: overlap check failed"
        - "Renesas ATF: image loading error"
        - "secure boot violation"
    condition: selection
falsepositives:
    - Legitimate firmware updates
level: high

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2024-6287 - Renesas ATF Memory Overlap Exploitation"; flow:to_server; content:"Renesas"; nocase; pcre:"/overlap|secure boot/i"; sid:1000001; rev:1;)

Remediation & Mitigation

1. Patch Application: Apply the official patch from Renesas as soon as it becomes available. Monitor Renesas security advisories for updates.
2. Firmware Integrity: Implement cryptographic verification of all loaded images using digital signatures.
3. Access Control: Restrict physical and local access to devices. Use secure boot with hardware root of trust.
4. Memory Protection: Enable Memory Protection Units (MPUs) to enforce strict memory region permissions.
5. Monitoring: Deploy detection rules (YARA, Sigma, Suricata) to identify exploitation attempts.
6. Incident Response: Prepare an incident response plan for compromised devices, including forensic analysis and re-imaging.

Valters IT
Securing Digital Frontiers