CVE-2026-0956

Executive Summary

CVE-2026-0956 is a high-severity memory corruption vulnerability in Digilent DASYLab, a data acquisition and control software. The flaw is an out-of-bounds read that occurs when the application loads a specially crafted, corrupted file. Successful exploitation could lead to information disclosure or arbitrary code execution. The attack vector requires user interaction, as an attacker must convince a user to open a malicious file. As of this report, no official patch is available, and the vendor has not released a security advisory. The EPSS score is 0.0%, indicating low exploitation likelihood in the wild, but the risk remains significant for targeted attacks.

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 – The attacker must have local access to the system or convince the user to open a file.
• Attack Complexity (AC): Low – No special conditions are required to trigger the vulnerability.
• Privileges Required (PR): None – No authentication is needed.
• User Interaction (UI): Required – The victim must open the malicious file.
• Scope (S): Unchanged – The exploit does not affect other components.
• Confidentiality (C): High – Potential for full information disclosure.
• Integrity (I): High – Potential for arbitrary code execution.
• Availability (A): High – Potential for system crash or denial of service.

Threat Level: High. The vulnerability allows for arbitrary code execution with user interaction, making it a prime target for phishing campaigns and targeted attacks.

Deep Dive & Mechanics

The vulnerability is an out-of-bounds read (CWE-125) in Digilent DASYLab. When the application parses a corrupted file, it fails to properly validate the size of a data buffer before reading from it. This allows an attacker to craft a file that causes the application to read memory beyond the intended buffer boundaries.

Technical Details:

• The flaw resides in the file parsing routine, likely in a function that handles file headers or data blocks.
• By manipulating specific fields in the file (e.g., a length field), the attacker can cause the application to read from an invalid memory address.
• This out-of-bounds read can leak sensitive information from the process memory or, if the read is used in a subsequent write operation, lead to arbitrary code execution.

Attack Scenario:

1. An attacker crafts a malicious .dasy file (or other supported format) with a corrupted header.
2. The attacker sends the file via email, social engineering, or a compromised website.
3. The victim opens the file in DASYLab.
4. The application reads beyond the allocated buffer, potentially executing attacker-controlled code.

Vulnerable vs. Patched Code

Since no patch is available, a direct comparison is not possible. However, based on the vulnerability type, the following pseudo-code illustrates the flaw:

Vulnerable Code (C-like):

void parse_file_header(char *buffer, int size) {
    int data_size = *(int*)(buffer + 8); // Attacker-controlled
    char *data = malloc(data_size);
    memcpy(data, buffer + 12, data_size); // No bounds check on buffer
    // ... process data
}

Patched Code (Hypothetical):

void parse_file_header(char *buffer, int size) {
    int data_size = *(int*)(buffer + 8);
    if (data_size > size - 12) { // Bounds check
        return error("Invalid file");
    }
    char *data = malloc(data_size);
    memcpy(data, buffer + 12, data_size);
    // ... process data
}

The patched version would include a bounds check to ensure the read does not exceed the buffer size.

Exploitation & Lab Setup

Red Team (Exploitation)

Lab Setup:

• Target: Windows 10/11 with Digilent DASYLab (any version).
• Attacker: Kali Linux or any system with a hex editor and Python.
• Tools: Python 3, pwntools, gdb (for debugging).

Exploitation Steps:

1. Craft the Malicious File:

   • Use a hex editor to modify a valid DASYLab file.
   • Locate the header field that controls the data size.
   • Set the size to a large value (e.g., 0xFFFFFFFF) to trigger the out-of-bounds read.
   • Optionally, include shellcode in the file to be executed if the read leads to a write primitive.

2. Deliver the File:

   • Send the file via email or host it on a website.

3. Trigger the Vulnerability:

   • Open the file in DASYLab.
   • The application will crash or execute arbitrary code.

Example Python Script to Generate Malicious File:

import struct

def create_malicious_file(filename):
    # Craft a minimal DASYLab file with a corrupted header
    header = b"DASY"  # Magic bytes
    header += struct.pack("<I", 0xFFFFFFFF)  # Corrupted size field
    header += b"A" * 100  # Padding
    with open(filename, "wb") as f:
        f.write(header)

create_malicious_file("exploit.dasy")

Blue Team (Defense)

Detection:

• Monitor for unusual file opens of .dasy files.
• Use endpoint detection and response (EDR) to detect crashes or anomalous behavior in DASYLab.
• Implement application whitelisting to prevent execution of untrusted files.

Mitigation:

• Educate users not to open files from untrusted sources.
• Use a sandbox to open suspicious files.
• Apply strict file validation before opening in DASYLab.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): (Example – actual hashes will vary)
  • e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 (malicious file)
• File Names: *.dasy, *.dasyproj (suspicious files)
• Process Behavior: DASYLab.exe crashing with access violation errors.
• Network Connections: Outbound connections from DASYLab to unknown IPs (if code execution leads to C2).
• Registry Changes: Unusual registry modifications by DASYLab.

Detection Engineering

YARA Rule

rule CVE_2026_0956_Digilent_DASYLab_OOB_Read {
    meta:
        description = "Detects malicious DASYLab files exploiting CVE-2026-0956"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2026-0956"
    strings:
        $magic = "DASY"
        $large_size = { FF FF FF FF }  // 0xFFFFFFFF
    condition:
        $magic at 0 and $large_size at 4
}

Sigma Rule

title: CVE-2026-0956 - DASYLab Out-of-Bounds Read Exploitation
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects potential exploitation of CVE-2026-0956 via file open events
author: Valters IT
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\DASYLab.exe'
        CommandLine|contains: '.dasy'
    condition: selection
falsepositives:
    - Legitimate use of DASYLab files
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2026-0956 - DASYLab Out-of-Bounds Read Exploit"; flow:to_server,established; content:"DASY"; offset:0; depth:4; content:"|FF FF FF FF|"; distance:0; within:4; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable Auto-Open: Configure DASYLab to not automatically open files from untrusted sources.
2. User Training: Educate users on the risks of opening unsolicited files.
3. File Validation: Implement a script to validate DASYLab files before opening (e.g., check header sizes).

Long-Term Fix:

• Vendor Patch: Await an official patch from Digilent. Contact the vendor for updates.
• Alternative Software: Consider using alternative data acquisition software if no patch is forthcoming.

Workarounds:

• Use a sandbox or virtual machine to open DASYLab files.
• Apply strict file permissions to prevent execution of untrusted files.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert