CVE-2025-29486

Executive Summary

CVE-2025-29486 identifies a memory leak vulnerability in libming v0.4.8, specifically within the parseSWF_PLACEOBJECT3 function. This flaw can lead to resource exhaustion, potentially causing a denial-of-service (DoS) condition in applications that process untrusted SWF files using the libming library. The vulnerability has a CVSS score of 0.0 (likely unassigned or placeholder), and no public exploit code or patch is currently available. The vendor, Libming, has not released a fix, and the project appears unmaintained.

Supply Chain & Package Security

libming is a C library used for parsing and generating SWF (Shockwave Flash) files. It is not distributed via typical package ecosystems like NPM, PyPI, Go, or Ruby, but is often included as a dependency in multimedia processing tools and legacy applications. The lack of a patch and the unmaintained status of the project pose a supply chain risk for any software that statically or dynamically links against libming. Organizations should inventory their use of libming and consider replacing it with maintained alternatives.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is unusual and likely indicates that the score has not been formally calculated or assigned by NVD. Based on the nature of the vulnerability (memory leak leading to DoS), a reasonable CVSS v3.1 vector would be:

• Attack Vector (AV): Local (L) – requires processing a malicious SWF file.
• Attack Complexity (AC): Low (L) – no special conditions.
• Privileges Required (PR): None (N) – no authentication needed.
• User Interaction (UI): Required (R) – user must open or process the file.
• Scope (S): Unchanged (U) – vulnerability does not cross trust boundaries.
• Confidentiality (C): None (N) – no data exposure.
• Integrity (I): None (N) – no data modification.
• Availability (A): High (H) – memory exhaustion can crash the application.

Estimated CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H Estimated Base Score: 5.5 (Medium)

Threat Level: Medium. The vulnerability requires local access or user interaction to exploit, and the impact is limited to availability.

Deep Dive & Mechanics

The vulnerability resides in the parseSWF_PLACEOBJECT3 function within libming's SWF parser. This function is responsible for handling the PlaceObject3 tag, which defines the placement of objects on the display list in a SWF file.

Root Cause: The function allocates memory for various data structures (e.g., for matrix, color transform, and filter data) but fails to properly free this memory in all code paths, particularly when encountering malformed or unexpected tag data. This leads to a memory leak.

Trigger: An attacker crafts a SWF file with a malicious PlaceObject3 tag that causes the parser to allocate memory without subsequent deallocation. Repeated processing of such files (or a single file with many such tags) will exhaust available memory, leading to a denial-of-service condition.

Impact: The primary impact is on availability. Applications using libming to parse SWF files (e.g., media players, converters, or web applications that process Flash content) could crash or become unresponsive. There is no evidence of code execution or data leakage.

Vulnerable vs. Patched Code

Since no official patch exists, the vulnerable code is in libming v0.4.8. The following is a conceptual comparison based on the vulnerability description.

Vulnerable Code (libming v0.4.8 - src/blocks/placeobject3.c):

void parseSWF_PLACEOBJECT3(SWF_Block block) {
    // ... parsing logic ...
    SWF_Matrix matrix = newSWF_Matrix();
    // ... allocate and use matrix ...
    // Memory leak: matrix is not freed on all exit paths
    if (error_condition) {
        return; // matrix leaked
    }
    // ... more allocations ...
}

Patched Code (Hypothetical Fix):

void parseSWF_PLACEOBJECT3(SWF_Block block) {
    SWF_Matrix matrix = NULL;
    // ... other pointers ...
    matrix = newSWF_Matrix();
    if (matrix == NULL) {
        // handle allocation failure
        return;
    }
    // ... parsing logic ...
    if (error_condition) {
        destroySWF_Matrix(matrix);
        // free other allocated resources
        return;
    }
    // ... use matrix ...
    destroySWF_Matrix(matrix);
    // free other allocated resources
}

The fix involves ensuring that all allocated memory is freed on every exit path, including error conditions.

Exploitation & Lab Setup

Red Team

Objective: Cause a denial-of-service condition in an application using libming v0.4.8.

Lab Setup:

1. Target: A system running an application that uses libming v0.4.8 (e.g., a custom SWF parser or a legacy media server).
2. Attacker Machine: Kali Linux or similar.

Steps:

1. Craft Malicious SWF: Create a SWF file with multiple PlaceObject3 tags that trigger the memory leak. This can be done using a hex editor or a scripting language like Python with the swf module.

   # Example Python script to generate a malicious SWF (simplified)
   import struct
   
   def create_malicious_swf():
       # SWF header (FWS + version + file length)
       header = b'FWS' + struct.pack('<B', 9) + struct.pack('<I', 0)
       # PlaceObject3 tag (tag type 70, long header)
       tag_type = 70
       tag_length = 100  # arbitrary
       tag_header = struct.pack('<H', (tag_type << 6) | 0x3F) + struct.pack('<I', tag_length)
       # Malicious payload (e.g., invalid matrix data)
       payload = b'\x00' * tag_length
       swf_data = header + tag_header + payload
       with open('malicious.swf', 'wb') as f:
           f.write(swf_data)
   
   create_malicious_swf()
   

2. Deliver Payload: Send the malicious.swf file to the target (e.g., via email, upload, or network share).
3. Trigger Processing: The target user or automated process opens the file with the vulnerable application.
4. Observe Impact: Monitor memory usage on the target. Repeated processing of the file will cause memory exhaustion, leading to application crash or system instability.

Blue Team

Detection and Mitigation:

1. Monitor Memory Usage: Set up alerts for abnormal memory consumption in applications that process SWF files.
2. Input Validation: If possible, validate SWF files before processing (e.g., check file size, structure, and tag counts).
3. Sandboxing: Run applications that parse untrusted SWF files in a sandboxed environment with limited memory.
4. Alternative Libraries: Replace libming with a maintained alternative (e.g., swftools or a custom parser) if feasible.

Indicators of Compromise (IOCs)

• File Hashes (Example):
  • malicious.swf SHA256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 (placeholder)
• Network Traffic: Unusual SWF file transfers (e.g., large number of SWF files or files with many PlaceObject3 tags).
• System Logs: Application crash logs or out-of-memory errors.
• Process Behavior: High memory usage by processes linked to libming.

Detection Engineering

YARA Rule

rule CVE_2025_29486_Memory_Leak_SWF {
    meta:
        description = "Detects SWF files with excessive PlaceObject3 tags indicative of CVE-2025-29486 exploitation"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-29486"
    strings:
        $tag_header = { 46 03 } // PlaceObject3 tag type (70 = 0x46) in little-endian
        $swf_magic = "FWS"
    condition:
        $swf_magic at 0 and #tag_header > 100 // Arbitrary threshold
}

Sigma Rule

title: CVE-2025-29486 Memory Leak via Malicious SWF
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects excessive memory usage by processes processing SWF files, indicating potential exploitation of CVE-2025-29486.
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\your_swf_parser.exe' # Replace with actual process name
        CommandLine|contains: '.swf'
    condition: selection
    timeframe: 5m
    condition: selection | count() by Image > 10 # High frequency of SWF processing
falsepositives:
    - Legitimate batch processing of SWF files
level: medium

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-29486 Potential Malicious SWF Transfer"; flow:to_server; content:"FWS"; offset:0; depth:3; content:"|46 03|"; distance:0; within:2; threshold: type both, track by_src, count 10, seconds 60; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate: If libming v0.4.8 is in use, isolate the affected systems from untrusted SWF file sources.
2. Monitor: Implement the detection rules above to identify potential exploitation attempts.
3. Workaround: If source code is available, apply a manual fix by ensuring all allocated memory is freed in parseSWF_PLACEOBJECT3 (see patched code example).

Long-Term Solutions:

1. Replace libming: Migrate to a maintained library for SWF parsing, such as swftools or a custom lightweight parser.
2. Upgrade: If a patched version of libming becomes available, upgrade immediately.
3. Vendor Contact: Attempt to contact the libming maintainers to request a fix or consider forking the project.

Valters IT