CVE-2025-7993

Executive Summary

CVE-2025-7993 is a critical Use-After-Free (UAF) vulnerability in Ashlar-Vellum Cobalt, a CAD/CAM software application. The flaw resides in the parsing of LI files, where the software fails to validate the existence of an object before performing operations on it. This allows an attacker to execute arbitrary code in the context of the current process by tricking a user into opening a malicious LI file or visiting a malicious page. The vulnerability has a CVSS score of 7.8 (High) and is currently unpatched. No public exploit code or proof-of-concept is available, but the risk is significant due to the potential for remote code execution.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a standalone desktop application (Ashlar-Vellum Cobalt) and does not involve software supply chain dependencies.

CVSS Breakdown & Threat Level

• CVSS Score: 7.8 (High)
• Attack Vector: Local (AV:L) – Requires user interaction to open a malicious file.
• Attack Complexity: Low (AC:L) – No special conditions needed.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: Required (UI:R) – Victim must open the file.
• Scope: Unchanged (S:U) – Exploit does not affect other components.
• Confidentiality Impact: High (C:H) – Full data access possible.
• Integrity Impact: High (I:H) – Code execution allows modification.
• Availability Impact: High (A:H) – Can crash or control the process.

Threat Level: High. Exploitation is straightforward if a user opens a crafted LI file. No patch exists, making all versions of Ashlar-Vellum Cobalt potentially vulnerable.

Deep Dive & Mechanics

The vulnerability is a classic Use-After-Free (CWE-416) in the LI file parser of Ashlar-Vellum Cobalt. LI files are used for storing 3D model data. The parser does not properly track object lifetimes, leading to a dangling pointer. When the parser attempts to dereference a freed object, an attacker can control the memory contents to achieve arbitrary code execution.

Root Cause: Lack of validation of object existence before use. The parser frees an object but retains a pointer to it, then later uses that pointer without checking if the memory is still valid.

Attack Vector: Remote, via a malicious LI file. The attacker must convince the user to open the file (e.g., via email, download, or web page). Once opened, the UAF triggers, allowing the attacker to execute shellcode in the context of the Cobalt process.

Impact: Full compromise of the user's system, including data theft, malware installation, or lateral movement within a network.

Vulnerable vs. Patched Code

Since no patch is available, a comparison cannot be made. However, the vulnerable code pattern is:

// Vulnerable pseudo-code
object* obj = parse_object(data);
free(obj);
// ... later ...
obj->method();  // Use-after-free: obj is dangling

A patched version would either set the pointer to NULL after freeing or use a reference-counting mechanism to ensure the object is not freed prematurely.

Exploitation & Lab Setup

Red Team (Attack Simulation)

Prerequisites:

• Ashlar-Vellum Cobalt installed on a target machine.
• Ability to deliver a malicious LI file (e.g., via phishing email).

Steps:

1. Craft a malicious LI file that triggers the UAF. This requires reverse engineering the LI file format and identifying the vulnerable code path.
2. Embed shellcode (e.g., a reverse shell) in the file.
3. Deliver the file to the victim (e.g., as an email attachment).
4. When the victim opens the file, the UAF triggers, and the shellcode executes.

Example (Conceptual):

# Python script to generate a malicious LI file (simplified)
import struct

def create_malicious_li():
    # Craft a malformed LI file that triggers UAF
    payload = b"\x00" * 100  # Placeholder for exploit data
    with open("exploit.li", "wb") as f:
        f.write(payload)

create_malicious_li()

Note: No public exploit exists; this is a conceptual guide.

Blue Team (Defense & Detection)

Detection:

• Monitor for unusual file opens of LI files from untrusted sources.
• Use endpoint detection and response (EDR) to detect memory corruption patterns (e.g., access violations).
• Deploy application whitelisting to block unknown executables.

Mitigation:

• Disable automatic opening of LI files in email clients.
• Use sandboxing or virtualized environments for opening untrusted CAD files.
• Apply strict file access controls.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): Unknown (no public samples).
• Network Indicators: Outbound connections from Cobalt process to attacker IPs (if reverse shell used).
• Process Behavior: Cobalt.exe crashes or exhibits abnormal memory access patterns.
• Registry/File System: Creation of suspicious files in temp directories.

Detection Engineering

YARA Rule

rule CVE_2025_7993_Ashlar_Vellum_LI_UAF {
    meta:
        description = "Detects malicious LI files targeting CVE-2025-7993"
        author = "Valters IT"
        date = "2025-04-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-7993"
    strings:
        $magic = { 4C 49 46 46 }  // "LIFF" magic bytes (example)
        $exploit_pattern = { 41 41 41 41 }  // Placeholder for exploit bytes
    condition:
        $magic at 0 and $exploit_pattern
}

Sigma Rule

title: CVE-2025-7993 Ashlar-Vellum Cobalt LI File Exploitation
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects potential exploitation of CVE-2025-7993 via LI file opening
author: Valters IT
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\cobalt.exe'
        CommandLine|contains: '.li'
    condition: selection
falsepositives:
    - Legitimate use of LI files
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET $HTTP_PORTS (
    msg:"CVE-2025-7993 Ashlar-Vellum Cobalt LI File Download";
    flow:to_server,established;
    content:"Content-Type|3a 20|application/octet-stream";
    content:".li";
    pcre:"/\.li$/U";
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. No patch available: Isolate systems running Ashlar-Vellum Cobalt from untrusted networks.
2. User awareness: Train users not to open LI files from unknown sources.
3. Application control: Use software restriction policies to block Cobalt from executing untrusted files.

Long-term:

• Monitor vendor for patches or workarounds.
• Consider migrating to alternative CAD software with active security support.
• Implement file integrity monitoring for LI files.

Workaround: If possible, convert LI files to a safer format (e.g., STEP) before opening.

Valters IT
Securing Digital Frontiers