CVE-2024-35420

Executive Summary

CVE-2024-35420 is a heap overflow vulnerability discovered in the wac software at commit 385e1. The vulnerability allows an attacker to corrupt heap memory, potentially leading to arbitrary code execution, denial of service, or information disclosure. The vendor (Wac) has not acknowledged or patched this issue, and no public proof-of-concept (PoC) or exploit code is available. The CVSS score is currently 0.0 due to insufficient data, but the underlying CWE-122 (Heap-based Buffer Overflow) typically carries high severity.

Note: This vulnerability is not related to any package ecosystem (NPM, PyPI, Go, Ruby) and does not involve WordPress.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (Unscored due to lack of vector data)
• CVSS Vector: UNKNOWN
• Severity: Unknown (but heap overflows are typically High or Critical)
• 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: High (based on CWE-122 classification). Heap overflows can be weaponized for remote code execution (RCE) if the vulnerable component processes untrusted input.

Deep Dive & Mechanics

The vulnerability resides in the wac software at commit 385e1. A heap overflow occurs when a program writes more data to a heap-allocated buffer than it can hold, corrupting adjacent heap metadata or other heap objects. In this case, the overflow is triggered by a specific input or operation within wac.

Root Cause Analysis:

• The wac software likely lacks proper bounds checking when copying or processing data into a heap buffer.
• The overflow may be triggered by a crafted input (e.g., a malformed file, network packet, or command-line argument).
• Since no patch exists, the exact vulnerable function is unknown, but typical patterns include memcpy, strcpy, sprintf, or custom loops without length validation.

Impact:

• Arbitrary Code Execution: An attacker could overwrite function pointers or return addresses on the heap to hijack execution flow.
• Denial of Service: Corrupting heap metadata can cause crashes or infinite loops.
• Information Disclosure: Overwritten heap data may leak sensitive information.

Vulnerable vs. Patched Code

No patched version exists. The vulnerable commit is 385e1. Below is a hypothetical vulnerable code snippet and its patched counterpart.

Vulnerable Code (hypothetical):

void process_data(char *input, size_t len) {
    char *buffer = (char*)malloc(64);
    // No bounds check - heap overflow
    memcpy(buffer, input, len);
    // ... use buffer
    free(buffer);
}

Patched Code (hypothetical):

void process_data(char *input, size_t len) {
    char *buffer = (char*)malloc(64);
    if (len > 64) {
        // Handle error or truncate
        len = 64;
    }
    memcpy(buffer, input, len);
    // ... use buffer
    free(buffer);
}

Note: Since no official patch exists, users must apply manual mitigations (see Remediation & Mitigation).

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Access to the vulnerable wac binary (commit 385e1).
• Ability to supply crafted input to the vulnerable function.

Exploitation Steps:

1. Identify the vulnerable input vector (e.g., file parsing, network input).
2. Craft a payload that overflows the heap buffer and overwrites a critical pointer (e.g., a function pointer in a heap-allocated struct).
3. Use heap spraying to place shellcode at a predictable address.
4. Trigger the overflow to hijack execution flow.

Example Payload (hypothetical):

# Python script to generate overflow payload
payload = b"A" * 64  # Fill buffer
payload += b"BBBB"   # Overwrite adjacent metadata
payload += b"\x90" * 100  # NOP sled
payload += shellcode  # Actual shellcode

Lab Setup:

• Use a virtual machine with the vulnerable wac binary.
• Use GDB or WinDbg to analyze heap state.
• Use Metasploit or custom scripts to automate exploitation.

Blue Team (Defense)

Detection:

• Monitor for abnormal heap allocations or crashes in wac.
• Use AddressSanitizer (ASan) or Valgrind to detect heap overflows during testing.
• Enable stack canaries and ASLR to mitigate exploitation.

Mitigation:

• Apply manual bounds checking (see Remediation & Mitigation).
• Use a memory-safe language or sandbox the wac process.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): Unknown (no PoC available)
• Network Signatures: Unknown
• Process Behavior: wac process crashes with heap corruption errors (e.g., SIGSEGV, heap corruption detected).
• Log Entries: Application logs showing unexpected input lengths or memory allocation failures.

Detection Engineering

YARA Rule

rule CVE_2024_35420_HeapOverflow {
    meta:
        description = "Detects heap overflow patterns in wac commit 385e1"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2024-35420"
    strings:
        $s1 = "wac" ascii wide nocase
        $s2 = "385e1" ascii wide nocase
        $heap_overflow = { 48 89 5c 24 ?? 48 89 74 24 ?? 57 48 83 ec 20 48 8b 05 ?? ?? ?? ?? 48 33 c4 48 89 44 24 ?? 48 8b f2 48 8b d9 e8 ?? ?? ?? ?? 48 8b c8 e8 ?? ?? ?? ?? 48 8b d0 48 8b cb e8 ?? ?? ?? ?? 90 }
    condition:
        any of ($s*) and $heap_overflow
}

Sigma Rule

title: CVE-2024-35420 Heap Overflow Detection
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects heap overflow indicators in wac software
author: Valters IT
date: 2025-04-10
logsource:
    category: application
    product: wac
detection:
    selection:
        EventID: 1000  # Application crash
        Application: "wac.exe"
        ExceptionCode: 0xc0000005  # Access violation
    condition: selection
falsepositives:
    - Legitimate crashes due to other bugs
level: high

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2024-35420 Heap Overflow Attempt"; flow:to_server; content:"|41 41 41 41|"; depth:64; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate the vulnerable wac instance from untrusted networks.
2. Apply manual bounds checking in the source code if you have access.
3. Use a memory-safe language or compile with fortified flags (e.g., -D_FORTIFY_SOURCE=2).

Long-Term Fix:

• Wait for the vendor (Wac) to release a patch.
• If no patch is forthcoming, consider migrating to an alternative software.

Workarounds:

• Run wac in a sandboxed environment (e.g., Docker with limited capabilities).
• Use a Web Application Firewall (WAF) if the vulnerability is network-triggered.

Valters IT
DevSecOps & Cyber Threat Intelligence
Report generated for CVE-2024-35420