CVE-2025-11463

Executive Summary

CVE-2025-11463 is a critical remote code execution vulnerability in Ashlar-Vellum Cobalt, a computer-aided design (CAD) software application. The flaw resides in the parsing of XE files, where improper validation of user-supplied data can trigger an integer overflow before a buffer allocation. This overflow can be exploited by an attacker to execute arbitrary code in the context of the current process. The vulnerability requires user interaction, such as opening a malicious XE file or visiting a malicious page. The CVSS score is 7.8 (High), and the EPSS score is 0.0%, indicating low exploitation likelihood at this time. No public proof-of-concept or patch is currently available.

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 (L) – The attacker must have local access or trick the user into opening a file.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): Required (R) – The victim must open a malicious file or visit a malicious page.
• Scope (S): Unchanged (U) – The vulnerability does not affect other components.
• Confidentiality (C): High (H) – Full data compromise possible.
• Integrity (I): High (H) – Full data modification possible.
• Availability (A): High (H) – Full system denial of service possible.

Threat Level: High. Although no active exploitation has been reported, the potential for arbitrary code execution in a widely used CAD application makes this a significant threat.

Deep Dive & Mechanics

The vulnerability is an integer overflow (CWE-190) in the parsing logic of XE files within Ashlar-Vellum Cobalt. When the software reads a specially crafted XE file, it fails to properly validate the size of user-supplied data. This can cause an integer overflow when calculating the buffer size needed for allocation. The overflow results in a smaller-than-expected buffer being allocated, leading to a heap-based buffer overflow when the data is copied. An attacker can leverage this to overwrite adjacent memory and achieve arbitrary code execution.

The specific flaw was reported via ZDI-CAN-26626. The vulnerability is triggered during the parsing of XE file structures, likely involving a length field that is not properly sanitized. The integer overflow occurs before the buffer allocation, meaning the software allocates a buffer that is too small, and subsequent write operations overflow it.

Vulnerable vs. Patched Code

No patched version is currently available. The vulnerable code is in the XE file parsing routine. A hypothetical fix would involve:

• Vulnerable Code (pseudo):

  uint32_t size = read_uint32(file);
  char *buffer = malloc(size); // Integer overflow if size is large
  read_data(file, buffer, size);
  

• Patched Code (pseudo):

  uint64_t size = read_uint32(file);
  if (size > MAX_BUFFER_SIZE) {
      return error;
  }
  char *buffer = malloc(size);
  if (buffer == NULL) {
      return error;
  }
  read_data(file, buffer, size);
  

The patch would include proper validation of the size field, using a larger integer type (e.g., uint64_t) and checking against a maximum allowed size before allocation.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Ashlar-Vellum Cobalt installed on a target system.
• Ability to deliver a malicious XE file to the target (e.g., via email, download, or USB).

Exploitation Steps:

1. Craft Malicious XE File: Create a specially crafted XE file that triggers the integer overflow. This involves setting a large value in a length field that causes the buffer allocation to be smaller than expected.
2. Deliver Payload: Send the malicious file to the target user, enticing them to open it.
3. Trigger Vulnerability: When the user opens the file in Ashlar-Vellum Cobalt, the integer overflow occurs, leading to a heap overflow.
4. Achieve Code Execution: The heap overflow overwrites critical data structures, allowing the attacker to execute arbitrary shellcode.

Example (Conceptual):

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

def create_malicious_xe():
    # Craft a malicious XE file with an oversized length field
    payload = b"A" * 1000  # Shellcode or ROP chain
    # Integer overflow: set length to 0xFFFFFFFF
    length_field = struct.pack("<I", 0xFFFFFFFF)
    # Build file structure
    with open("malicious.xe", "wb") as f:
        f.write(b"XE")  # Magic bytes
        f.write(length_field)
        f.write(payload)

create_malicious_xe()

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

Blue Team (Defense)

Detection:

• Monitor for unusual file downloads or email attachments with .xe extension.
• Use endpoint detection and response (EDR) to monitor for heap corruption or abnormal memory allocations in Ashlar-Vellum Cobalt.
• Implement application whitelisting to prevent execution of untrusted files.

Mitigation:

• Disable automatic file preview or parsing of XE files if possible.
• Use sandboxing or virtualization to open untrusted CAD files.
• Apply the principle of least privilege to user accounts.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): (None available yet, but monitor for malicious XE files)
• Network Indicators: Connections to unknown IPs or domains after file opening.
• Process Behavior: Ashlar-Vellum Cobalt process (e.g., cobalt.exe) exhibiting abnormal memory allocation or crashes.
• Registry/File System: Creation of suspicious files in temporary directories.

Detection Engineering

YARA Rule

rule CVE_2025_11463_XE_IntegerOverflow {
    meta:
        description = "Detects malicious XE files exploiting CVE-2025-11463"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-11463"
    strings:
        $magic = "XE"
        $large_size = { FF FF FF FF }  // Potential integer overflow trigger
    condition:
        $magic at 0 and $large_size
}

Sigma Rule

title: CVE-2025-11463 Exploitation Attempt
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects potential exploitation of CVE-2025-11463 via malicious XE file
author: Valters IT
date: 2025-04-10
logsource:
    category: file_event
    product: windows
detection:
    selection:
        TargetFilename|endswith: '.xe'
        Image|endswith: 'cobalt.exe'
    condition: selection
falsepositives:
    - Legitimate XE files from trusted sources
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-11463 XE File Download"; flow:to_server,established; content:"|58 45|"; depth:2; content:"|FF FF FF FF|"; distance:2; within:4; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

• Patch: No official patch is available. Monitor Ashlar-Vellum for updates.
• Workaround: Avoid opening XE files from untrusted sources. Use a dedicated, isolated environment for CAD file processing.
• Mitigation: Implement strict file upload validation on web applications that accept XE files. Use network segmentation to limit exposure.
• Detection: Deploy the provided YARA, Sigma, and Suricata rules to detect malicious XE files.

Valters IT
DevSecOps & Cyber Threat Intelligence