CVE-2025-7998

Executive Summary

CVE-2025-7998 is a critical Out-Of-Bounds Write vulnerability in Ashlar-Vellum Cobalt, a computer-aided design (CAD) application. The flaw resides in the parsing of CO files, where insufficient validation of user-supplied data allows an attacker to write past the end of an allocated data structure. Successful exploitation requires user interaction (opening a malicious file or visiting a malicious page) and can lead to remote code execution in the context of the current process. The vulnerability was reported via ZDI-CAN-26046 and currently has no known patch or public exploit code. The EPSS score is 0.0%, indicating low exploitation activity in the wild, but the risk remains high due to the potential for full system compromise.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby ecosystems. It affects a standalone desktop application (Ashlar-Vellum Cobalt) and is distributed via traditional software channels. No supply chain package security implications are present.

CVSS Breakdown & Threat Level

• CVSS Score: 7.8 (High)
• Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
• Attack Vector (AV): Local (requires opening a file)
• Attack Complexity (AC): Low
• Privileges Required (PR): None
• User Interaction (UI): Required (victim must open malicious file)
• Scope (S): Unchanged
• Confidentiality (C): High
• Integrity (I): High
• Availability (A): High

Threat Level: High. Although no active exploitation has been observed, the vulnerability allows arbitrary code execution with minimal user interaction. The lack of a patch increases the risk for organizations using Ashlar-Vellum Cobalt.

Deep Dive & Mechanics

The vulnerability is a classic Out-Of-Bounds Write (CWE-787) occurring during the parsing of CO files. CO files are proprietary CAD format files used by Ashlar-Vellum Cobalt. The specific flaw is in the file parsing routine where the application reads user-supplied data from the CO file without proper bounds checking. When processing a crafted CO file, the application writes data beyond the allocated buffer, corrupting adjacent memory. This can be leveraged by an attacker to overwrite critical data structures, such as function pointers or return addresses, leading to arbitrary code execution.

Root Cause: Lack of validation of the size or offset fields within the CO file structure, causing the parser to write beyond the intended buffer.

Attack Vector: The attacker delivers a malicious CO file via email, download, or other means. The victim must open the file with Ashlar-Vellum Cobalt. No additional privileges are required.

Impact: Successful exploitation allows the attacker to execute arbitrary code with the same privileges as the current user. This can lead to data theft, installation of malware, or further compromise of the system.

Vulnerable vs. Patched Code

Since no patch is available, a direct code comparison is not possible. However, the vulnerable code likely resembles:

// Vulnerable pseudo-code
void parse_CO_file(char *data, size_t size) {
    char *buffer = malloc(256);
    int offset = *(int*)data; // read offset from file
    memcpy(buffer + offset, data + 4, size - 4); // no bounds check on offset
}

A patched version would include bounds checking:

// Patched pseudo-code
void parse_CO_file(char *data, size_t size) {
    char *buffer = malloc(256);
    int offset = *(int*)data;
    if (offset < 0 || offset + (size - 4) > 256) {
        // handle error
        return;
    }
    memcpy(buffer + offset, data + 4, size - 4);
}

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• Ashlar-Vellum Cobalt installed (any version)
• Ability to craft a malicious CO file

Exploitation Steps:

1. Craft Malicious CO File: Use a hex editor or custom script to create a CO file with a crafted offset field that causes an out-of-bounds write. Overwrite a function pointer or return address to redirect execution to shellcode.
2. Deliver File: Send the malicious CO file to the target via email, download link, or physical media.
3. Trigger Exploit: The victim opens the file with Ashlar-Vellum Cobalt. The vulnerable parsing routine executes, leading to code execution.

Example Payload (Conceptual):

# Python script to generate a malicious CO file (conceptual)
import struct

# Craft offset to overwrite return address
offset = 0x41414141  # Example offset
shellcode = b"\x90" * 100  # NOP sled + shellcode

with open("malicious.co", "wb") as f:
    f.write(struct.pack("<I", offset))
    f.write(shellcode)

Note: No public exploit code is available. This is a conceptual example.

Blue Team (Defensive)

Detection:

• Monitor for unusual file opens of CO files, especially from untrusted sources.
• Use endpoint detection and response (EDR) to detect memory corruption events (e.g., access violations, buffer overflow exceptions).
• Deploy application whitelisting to prevent execution of untrusted binaries.

Mitigation:

• Disable automatic file parsing for CO files if possible.
• Use sandboxing or virtualization to open untrusted files.
• Apply strict file access controls and user training to avoid opening suspicious files.

Indicators of Compromise (IOCs)

• File Hashes: (No known samples; placeholder)
  • malicious.co SHA256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
• Network Indicators: None specific to this CVE.
• Behavioral Indicators:
  • Ashlar-Vellum Cobalt process crash or access violation.
  • Unexpected child processes spawned from Cobalt.exe.
  • Memory regions with RWX permissions after file open.

Detection Engineering

YARA Rule

rule CVE_2025_7998_CO_File_Exploit {
    meta:
        description = "Detects malicious CO files exploiting CVE-2025-7998"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-7998"
    strings:
        $co_magic = { 43 4F 46 46 } // "COFF" magic bytes (example)
        $suspicious_offset = { 41 41 41 41 } // Example offset pattern
    condition:
        $co_magic at 0 and $suspicious_offset
}

Sigma Rule

title: CVE-2025-7998 Ashlar-Vellum Cobalt CO File Exploit
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects potential exploitation of CVE-2025-7998 via CO file parsing
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\Cobalt.exe'
        CommandLine|contains: '.co'
    condition: selection
falsepositives:
    - Legitimate use of CO files
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-7998 Ashlar-Vellum Cobalt CO File Download"; flow:to_server,established; content:"|43 4F 46 46|"; offset:0; depth:4; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate Systems: Disconnect affected systems from the network if possible.
2. User Training: Educate users not to open CO files from untrusted sources.
3. Application Control: Use software restriction policies to block execution of Cobalt.exe if not needed.

Long-Term Fix:

• Vendor Patch: Await an official patch from Ashlar-Vellum. Monitor their security advisories.
• Alternative Software: Consider using alternative CAD software that is actively maintained.
• Virtualization: Run Ashlar-Vellum Cobalt in a sandboxed environment (e.g., Windows Sandbox, VMware) to contain potential exploits.

Workarounds:

• Disable file association for .co files to prevent automatic opening.
• Use file scanning tools to detect malicious CO files before opening.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert