CVE-2024-27527

Executive Summary

CVE-2024-27527 is a Denial of Service (DoS) vulnerability identified in the Wasm3 WebAssembly interpreter, specifically in commit 139076a. The vulnerability allows an attacker to cause the application to crash or become unresponsive by providing a specially crafted WebAssembly binary. This can lead to service disruption in environments where Wasm3 is used to execute untrusted WebAssembly modules, such as edge computing, IoT devices, or sandboxed execution contexts.

The vulnerability is classified under CWE-400 (Uncontrolled Resource Consumption), indicating that the issue stems from improper handling of resource allocation or exhaustion. No public proof-of-concept (PoC) or exploit code is currently available, and the patch status remains unknown. The EPSS score is 0.0%, suggesting low exploitation activity in the wild at the time of analysis.

Supply Chain & Package Security

Wasm3 is an open-source WebAssembly interpreter written in C, commonly used in embedded systems, edge computing, and sandboxed environments. The vulnerability affects the specific commit 139076a, which may be included in various distributions or container images. Organizations using Wasm3 should verify their version and consider updating to a newer commit or applying mitigations.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is unusual and likely indicates that the score has not been officially assigned or calculated. Based on the nature of the vulnerability (DoS), a reasonable estimated CVSS v3.1 vector would be:

• Attack Vector (AV): Network (N) – The vulnerability can be triggered remotely by sending a crafted WebAssembly binary.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – The vulnerability does not affect other components.
• Confidentiality (C): None (N) – No data exposure.
• Integrity (I): None (N) – No data modification.
• Availability (A): High (H) – Complete loss of availability.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Threat Level: Medium to High, depending on the deployment context. In environments where Wasm3 processes untrusted WebAssembly modules, the risk is elevated.

Deep Dive & Mechanics

The vulnerability in Wasm3 commit 139076a is a Denial of Service (DoS) issue that likely arises from improper validation or resource management when parsing or executing a malicious WebAssembly binary. WebAssembly modules contain sections such as types, functions, memories, and tables. A crafted module can cause the interpreter to enter an infinite loop, allocate excessive memory, or trigger a crash due to a null pointer dereference or stack overflow.

The specific mechanism is not publicly documented, but common patterns for DoS in interpreters include:

• Infinite loops due to malformed control flow instructions.
• Memory exhaustion from repeated allocation requests.
• Stack overflow from deeply nested function calls.
• Integer overflow leading to buffer overflows.

Given the lack of a patch, the vulnerability remains unaddressed in the affected commit. Users are advised to monitor the Wasm3 repository for updates or apply mitigations such as input validation and resource limits.

Vulnerable vs. Patched Code

No patched version is currently available. The vulnerable commit is 139076a. Users should check the Wasm3 repository for any subsequent commits that may address this issue. If a patch becomes available, it would likely involve adding bounds checks, input validation, or resource limits in the WebAssembly parser or execution engine.

Exploitation & Lab Setup

Red Team

Since no public exploit code is available, a red team would need to reverse-engineer the vulnerability by analyzing the Wasm3 source code at commit 139076a. The following steps outline a potential approach:

1. Set up a lab environment with Wasm3 compiled from commit 139076a.
2. Fuzz the interpreter with malformed WebAssembly binaries using tools like wasm-tools or custom fuzzers.
3. Identify crash conditions and develop a minimal WebAssembly binary that triggers the DoS.
4. Test the exploit against the target service to confirm denial of service.

Example command to compile Wasm3:

git clone https://github.com/wasm3/wasm3.git
cd wasm3
git checkout 139076a
mkdir build && cd build
cmake .. && make

Blue Team

Blue teams should focus on detection and mitigation:

1. Monitor for unusual resource consumption (CPU, memory) in processes running Wasm3.
2. Implement input validation for WebAssembly binaries before execution.
3. Use resource limits (e.g., cgroups, ulimit) to contain potential DoS impact.
4. Deploy WebAssembly sandboxing with additional layers of security (e.g., seccomp, AppArmor).
5. Update Wasm3 to a newer commit if a patch becomes available.

Indicators of Compromise (IOCs)

• File Hashes: No specific hashes available.
• Network Indicators: No specific IPs or domains.
• Behavioral Indicators:
  • Wasm3 process consuming 100% CPU or excessive memory.
  • Repeated crashes or restarts of Wasm3.
  • Log entries indicating segmentation faults or out-of-memory errors.

Detection Engineering

YARA Rule

rule CVE_2024_27527_Wasm3_DoS {
    meta:
        description = "Detects potentially malicious WebAssembly binaries targeting Wasm3 CVE-2024-27527"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-27527"
    strings:
        $wasm_magic = { 00 61 73 6D }  // WebAssembly magic number
        $suspicious_section = { 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F }
    condition:
        $wasm_magic at 0 and #suspicious_section > 5
}

Sigma Rule

title: Wasm3 Denial of Service Exploit Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects potential exploitation of CVE-2024-27527 targeting Wasm3
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/wasm3'
        CommandLine|contains: '--run'
    condition: selection
falsepositives:
    - Legitimate use of Wasm3 with WebAssembly modules
level: medium

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2024-27527 Wasm3 DoS Attempt"; flow:to_server,established; content:"|00 61 73 6D|"; depth:4; content:"|01|"; within:10; reference:cve,2024-27527; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

1. Update Wasm3 to a version newer than commit 139076a if a patch becomes available.
2. Apply resource limits using operating system controls (e.g., ulimit, cgroups) to prevent resource exhaustion.
3. Implement input validation for WebAssembly binaries, rejecting malformed or suspicious modules.
4. Use WebAssembly sandboxing with additional security layers (e.g., seccomp, AppArmor).
5. Monitor logs for signs of exploitation and respond accordingly.

Valters IT
DevSecOps & Cyber Threat Intelligence