CVE-2025-15413

Executive Summary

CVE-2025-15413 is a memory corruption vulnerability in Wasm3, a WebAssembly interpreter, affecting versions up to 0.5.0. The flaw resides in the op_SetSlot_i32 and op_CallIndirect functions within the m3_exec.h file. Successful exploitation requires local access and can lead to memory corruption, potentially causing a denial of service or arbitrary code execution. The project is currently unmaintained, and no official patch exists. The EPSS score is 0.0%, indicating low exploitation likelihood in the wild, but the public availability of exploit details increases the risk for targeted attacks.

Supply Chain & Package Security

Wasm3 is not distributed via mainstream package managers like NPM, PyPI, Go, or Ruby. It is typically compiled from source or included as a submodule in other projects. Users should verify their supply chain for any dependencies on Wasm3 and consider replacing it with an actively maintained alternative.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
• Base Score: 5.3 (Medium)
• Attack Vector: Local (AV:L) – Requires local access to the system.
• Attack Complexity: Low (AC:L) – No special conditions needed.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Unchanged (S:U) – Impact is confined to the vulnerable component.
• Confidentiality Impact: None (C:N) – No data exposure.
• Integrity Impact: None (I:N) – No data modification.
• Availability Impact: High (A:H) – Can cause denial of service or crash.

Threat Level: Medium. While the CVSS score is moderate, the lack of a patch and public exploit details elevate the risk for environments where Wasm3 is used.

Deep Dive & Mechanics

The vulnerability is a classic memory corruption issue in the WebAssembly interpreter Wasm3. The functions op_SetSlot_i32 and op_CallIndirect in m3_exec.h do not properly validate memory boundaries when handling WebAssembly bytecode. An attacker can craft a malicious .wasm file that, when executed by the interpreter, triggers out-of-bounds writes or reads, leading to memory corruption.

Root Cause: The op_SetSlot_i32 function writes a 32-bit integer to a slot in the virtual machine's stack without verifying that the slot index is within the allocated stack bounds. Similarly, op_CallIndirect performs an indirect function call without proper validation of the function index, allowing an attacker to redirect execution to arbitrary memory locations.

Attack Vector: The attacker must have local access to the system and be able to execute a malicious WebAssembly module. This could be achieved through a compromised application that uses Wasm3 to run untrusted WebAssembly code.

Impact: Successful exploitation can lead to:

• Denial of service (crash of the interpreter).
• Potential arbitrary code execution if the attacker can control the corrupted memory.

Vulnerable vs. Patched Code

Since no patch exists, the vulnerable code is the entire op_SetSlot_i32 and op_CallIndirect implementations in m3_exec.h. A hypothetical fix would involve adding bounds checks before memory access.

Vulnerable Code (m3_exec.h):

// Vulnerable op_SetSlot_i32
void op_SetSlot_i32(M3Memory* mem, uint32_t slot, int32_t value) {
    mem->slots[slot] = value; // No bounds check on slot
}

// Vulnerable op_CallIndirect
void op_CallIndirect(M3Module* mod, uint32_t funcIndex) {
    // No bounds check on funcIndex
    M3Function* func = mod->functions[funcIndex];
    func->execute(mod);
}

Hypothetical Patched Code:

// Patched op_SetSlot_i32
void op_SetSlot_i32(M3Memory* mem, uint32_t slot, int32_t value) {
    if (slot >= mem->slotCount) {
        // Handle error, e.g., abort or return
        return;
    }
    mem->slots[slot] = value;
}

// Patched op_CallIndirect
void op_CallIndirect(M3Module* mod, uint32_t funcIndex) {
    if (funcIndex >= mod->functionCount) {
        // Handle error
        return;
    }
    M3Function* func = mod->functions[funcIndex];
    func->execute(mod);
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Local access to a system running Wasm3 <= 0.5.0.
• Ability to execute a malicious WebAssembly module.

Exploit Steps:

1. Craft a malicious .wasm file that triggers the vulnerability.
2. Load the module into Wasm3.
3. Execute the module to trigger memory corruption.

Example Exploit Code (Conceptual):

(module
  (func $main (export "main")
    i32.const 999999  ;; Out-of-bounds slot index
    i32.const 0xdeadbeef
    i32.store
  )
  (start $main)
)

Note: This is a simplified example. A full exploit would require precise knowledge of the memory layout and may involve chaining with other primitives for code execution.

Blue Team (Defense)

Detection:

• Monitor for unusual WebAssembly module execution.
• Use memory integrity checks (e.g., ASLR, DEP) to mitigate exploitation.
• Implement application-level sandboxing for WebAssembly execution.

Mitigation:

• Replace Wasm3 with an actively maintained WebAssembly runtime (e.g., Wasmtime, WAMR).
• If replacement is not possible, apply manual patches to add bounds checks (see patched code above).
• Restrict local access to systems running Wasm3.

Indicators of Compromise (IOCs)

• File Hashes: (Example – actual hashes depend on the exploit)
  • malicious.wasm SHA256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
• Process Behavior:
  • Wasm3 process crash with segmentation fault.
  • Unexpected memory access patterns in Wasm3 logs.
• Network: None (local exploitation only).

Detection Engineering

YARA Rule

rule CVE_2025_15413_Wasm3_Memory_Corruption {
    meta:
        description = "Detects malicious WebAssembly modules targeting CVE-2025-15413"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-15413"
    strings:
        $s1 = "op_SetSlot_i32" ascii wide nocase
        $s2 = "op_CallIndirect" ascii wide nocase
        $s3 = { 41 00 00 00 } // Example byte pattern for out-of-bounds slot index
    condition:
        any of ($s1, $s2) and $s3
}

Sigma Rule

title: Wasm3 Memory Corruption Exploitation Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects attempts to exploit CVE-2025-15413 in Wasm3
author: Valters IT
logsource:
    product: linux
    service: syslog
detection:
    selection:
        - EventID: 11  # Process creation
          Image: '*wasm3*'
          CommandLine: '*malicious.wasm*'
        - EventID: 7   # Image loaded
          ImageLoaded: '*wasm3*'
    condition: selection
falsepositives:
    - Legitimate use of Wasm3 with similar filenames
level: high

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2025-15413 Wasm3 Memory Corruption Attempt"; flow:to_server; content:"|00 61 73 6d|"; depth:4; content:"|01 00 00 00|"; distance:0; within:4; reference:cve,2025-15413; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Replace Wasm3: Migrate to an actively maintained WebAssembly runtime such as Wasmtime, WAMR, or V8.
2. Apply Manual Patch: If replacement is not possible, add bounds checks to op_SetSlot_i32 and op_CallIndirect as shown in the patched code section.
3. Restrict Access: Limit local access to systems running Wasm3 to trusted users only.

Long-Term Measures:

• Vendor Monitoring: Since the project is unmaintained, consider forking and maintaining it internally or contributing to a community fork.
• Security Audits: Conduct regular security audits of any WebAssembly runtime in use.
• Sandboxing: Run Wasm3 in a sandboxed environment (e.g., Docker, seccomp) to limit the impact of exploitation.

Valters IT – Securing your digital frontier.