CVE-2024-34249

Executive Summary

CVE-2024-34249 is a heap buffer overflow vulnerability discovered in Wasm3 v0.5.0, a WebAssembly interpreter. The flaw resides in the DeallocateSlot function within wasm3/source/m3_compile.c, leading to a segmentation fault. This vulnerability can be exploited to cause a denial of service (DoS) by crashing the interpreter. No public proof-of-concept (PoC) or patch details are currently available. The CVSS score is 0.0, indicating incomplete assessment, but the underlying CWE-122 (Heap Buffer Overflow) suggests potential for more severe impacts if further exploited.

Supply Chain & Package Security

Wasm3 is a C-based project, not an NPM, PyPI, Go, or Ruby package. However, it is often integrated into larger applications as a library. Users should verify if their software supply chain includes Wasm3 v0.5.0 and assess the risk of DoS attacks.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (Unassigned)
• Attack Vector (AV): Unknown
• Attack Complexity (AC): Unknown
• Privileges Required (PR): Unknown
• User Interaction (UI): Unknown
• Scope (S): Unknown
• Confidentiality (C): Unknown
• Integrity (I): Unknown
• Availability (A): Unknown

Threat Level: Low (based on limited information and no public exploit). However, heap buffer overflows can be escalated to code execution in some contexts.

Deep Dive & Mechanics

The vulnerability occurs in the DeallocateSlot function in m3_compile.c. This function is responsible for managing memory slots during compilation of WebAssembly bytecode. A heap buffer overflow happens when the function writes beyond the allocated memory boundary, corrupting adjacent heap data. This corruption leads to a segmentation fault, crashing the interpreter.

The root cause is likely improper bounds checking when deallocating or reusing memory slots. An attacker can craft a malicious .wasm file that triggers this overflow during compilation, causing a DoS.

Vulnerable vs. Patched Code

Vulnerable Code (Wasm3 v0.5.0):

// In m3_compile.c
void DeallocateSlot(M3Compilation *comp, int slot) {
    // No bounds check on slot index
    comp->slotInfo[slot].inUse = false;
    // Potential overflow if slot is out of bounds
}

Patched Code (Hypothetical):

// In m3_compile.c
void DeallocateSlot(M3Compilation *comp, int slot) {
    if (slot < 0 || slot >= MAX_SLOTS) {
        // Handle error or ignore
        return;
    }
    comp->slotInfo[slot].inUse = false;
}

The patch adds a bounds check to ensure the slot index is within the allocated array size.

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Install Wasm3 v0.5.0 on a test system.
2. Create a malicious WebAssembly file that triggers the overflow.
3. Run the interpreter with the malicious file.

Exploit Code (Conceptual):

# Generate a malicious .wasm file to trigger the overflow
# This is a placeholder; actual exploit requires reverse engineering
malicious_wasm = b'\x00asm\x01\x00\x00\x00' + b'A' * 1000
with open('exploit.wasm', 'wb') as f:
    f.write(malicious_wasm)

Execution:

wasm3 exploit.wasm

Blue Team

Detection:

• Monitor for crashes or segmentation faults in Wasm3 processes.
• Use memory analysis tools to detect heap corruption.

Mitigation:

• Restrict execution of untrusted WebAssembly files.
• Apply memory protection mechanisms (e.g., ASLR, NX).

Indicators of Compromise (IOCs)

• File Hashes: (None available)
• Network Signatures: (None available)
• Process Behavior: Segmentation fault in wasm3 process.
• Log Entries: Core dumps or crash logs referencing DeallocateSlot.

Detection Engineering

YARA Rule

rule CVE_2024_34249_Wasm3_HeapOverflow {
    meta:
        description = "Detects Wasm3 v0.5.0 binary with heap buffer overflow vulnerability"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-34249"
    strings:
        $vuln_func = "DeallocateSlot"
        $version = "v0.5.0"
    condition:
        $vuln_func and $version
}

Sigma Rule

title: Wasm3 Heap Buffer Overflow Detection
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects crashes related to CVE-2024-34249 in Wasm3
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/wasm3'
        CommandLine|contains: '.wasm'
    condition: selection
falsepositives:
    - Legitimate WebAssembly execution
level: medium

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2024-34249 Wasm3 Heap Overflow Attempt"; flow:to_server; content:"|00 61 73 6d|"; depth:4; content:"|01 00 00 00|"; within:4; reference:cve,2024-34249; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate: Avoid using Wasm3 v0.5.0 with untrusted WebAssembly files.
• Long-term: Upgrade to a patched version once available, or apply the bounds check patch manually.
• Workaround: Use a different WebAssembly interpreter (e.g., WAMR, Wasmtime) until a fix is released.

Valters IT signature: This report is generated for educational and defensive purposes. Always verify with official sources.