CVE-2024-25431

Executive Summary

CVE-2024-25431 is a privilege escalation vulnerability in the Bytecode Alliance's wasm-micro-runtime (WAMR) project, affecting versions prior to commit b3f728c. The flaw resides in the check_was_abi_compatibility function, which improperly validates crafted WebAssembly (WASM) files. A remote attacker can exploit this by supplying a malicious WASM binary, leading to arbitrary code execution or privilege escalation within the runtime environment. The vulnerability is unpatched in affected versions, with a fix available in commit 06df58f. No public proof-of-concept (PoC) or exploit code has been released, and the EPSS score is 0.0%, indicating low exploitation activity currently.

Supply Chain & Package Security

WAMR is a critical component in IoT, edge computing, and embedded systems, often distributed as a library or runtime. Organizations using WAMR in their supply chain must verify they are using a patched version (commit 06df58f or later). The vulnerability can be introduced via third-party WASM modules, making it essential to validate all WASM binaries before execution. No known malicious packages have been reported, but the risk of supply chain attacks via compromised WASM files remains.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (No official vector assigned)
• Attack Vector (AV): Network (likely)
• Attack Complexity (AC): Low (likely)
• Privileges Required (PR): None (likely)
• User Interaction (UI): None (likely)
• Scope (S): Unchanged (likely)
• Confidentiality (C): High (likely)
• Integrity (I): High (likely)
• Availability (A): High (likely)

Threat Level: Critical (based on remote exploitation potential and lack of authentication requirements)

Deep Dive & Mechanics

The vulnerability exists in the check_was_abi_compatibility function within WAMR's ABI (Application Binary Interface) compatibility checker. This function is invoked when loading a WASM module to verify that the module's ABI matches the runtime's expectations. The flaw stems from improper input validation: the function does not adequately sanitize or bounds-check data from the WASM binary, allowing an attacker to craft a malicious module that triggers a buffer overflow, use-after-free, or other memory corruption.

Root Cause: The check_was_abi_compatibility function reads ABI-related metadata from the WASM binary without verifying the size or validity of the data. An attacker can supply a specially crafted WASM file that causes the runtime to read out-of-bounds memory or write to arbitrary locations, leading to code execution.

Attack Vector: Remote, via network delivery of a malicious WASM file (e.g., through a web application, IoT device, or edge server that processes WASM modules).

Impact: Successful exploitation allows an attacker to execute arbitrary code with the privileges of the WAMR process, potentially leading to full system compromise.

Vulnerable vs. Patched Code

Vulnerable Code (before commit b3f728c):

// Simplified vulnerable function
bool check_was_abi_compatibility(const uint8_t *wasm_binary, size_t size) {
    // No bounds checking on ABI data
    uint32_t abi_version = *(uint32_t*)(wasm_binary + offset);
    // ... process abi_version without validation
}

Patched Code (commit 06df58f):

// Patched version with bounds checking
bool check_was_abi_compatibility(const uint8_t *wasm_binary, size_t size) {
    if (offset + sizeof(uint32_t) > size) {
        return false; // Prevent out-of-bounds read
    }
    uint32_t abi_version = *(uint32_t*)(wasm_binary + offset);
    // ... validate abi_version range
}

The patch adds a size check before reading ABI data, preventing out-of-bounds access.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• WAMR version prior to commit b3f728c
• Ability to deliver a malicious WASM file to the target

Steps:

1. Craft a WASM binary with a malformed ABI section that triggers the vulnerability.
2. Deliver the file via network (e.g., HTTP, file upload, or direct injection).
3. The check_was_abi_compatibility function processes the malicious data, leading to memory corruption.
4. Use a ROP chain or shellcode to escalate privileges or execute arbitrary commands.

Example (Conceptual):

# Python script to generate a malicious WASM file
import struct

def create_malicious_wasm():
    # Craft a WASM binary with oversized ABI data
    wasm_header = b'\x00asm\x01\x00\x00\x00'
    # Malicious ABI section
    abi_section = b'\x01' * 0x1000  # Trigger overflow
    return wasm_header + abi_section

with open('malicious.wasm', 'wb') as f:
    f.write(create_malicious_wasm())

Blue Team (Defense)

Detection:

• Monitor for unusual WASM files being loaded by WAMR processes.
• Use file integrity monitoring to detect tampered WASM binaries.
• Enable logging in WAMR to capture ABI compatibility errors.

Mitigation:

• Immediately update to commit 06df58f or later.
• Implement network segmentation to limit exposure of WAMR instances.
• Use application whitelisting to allow only trusted WASM modules.

Indicators of Compromise (IOCs)

• File Hashes: (None publicly available; generate your own for malicious samples)
• Network Signatures: WASM files with abnormally large or malformed ABI sections
• Process Behavior: WAMR process crashes or unexpected memory access patterns
• Log Entries: ABI compatibility check failures or segmentation faults in WAMR logs

Detection Engineering

YARA Rule

rule CVE_2024_25431_WAMR_ABI_Exploit {
    meta:
        description = "Detects malicious WASM files targeting CVE-2024-25431"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-25431"
    strings:
        $wasm_magic = { 00 61 73 6D }  // WASM magic bytes
        $abi_section = { 01 }          // ABI section ID (example)
    condition:
        $wasm_magic at 0 and #abi_section > 10  // Unusually many ABI sections
}

Sigma Rule

title: CVE-2024-25431 WAMR ABI Exploitation Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects attempts to exploit CVE-2024-25431 via malicious WASM files
author: Valters IT
logsource:
    product: linux
    service: syslog
detection:
    selection:
        - EventID: 11  # File creation
          Image: '*iwasm*'
          TargetFilename: '*.wasm'
        - EventID: 7   # Process creation
          Image: '*iwasm*'
          CommandLine: '*malicious*'
    condition: selection
falsepositives:
    - Legitimate WASM file loading
level: high

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2024-25431 WAMR ABI Exploit Attempt"; flow:to_server; content:"|00 61 73 6D|"; offset:0; depth:4; content:"|01|"; within:100; byte_test:4,>,1000,0; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Update WAMR to commit 06df58f or later.
2. If patching is not possible, restrict network access to WAMR instances.
3. Validate all WASM files before loading using a sandbox or static analysis.

Long-term Measures:

• Implement input validation for all WASM binary sections.
• Enable ASLR and DEP on systems running WAMR.
• Conduct regular security audits of WAMR deployments.

Workarounds:

• Disable ABI compatibility checking if not required (not recommended).
• Use a WebAssembly firewall to filter malicious modules.

Valters IT
Securing Digital Frontiers