CVE-2024-5581

Executive Summary

CVE-2024-5581 is a critical directory traversal vulnerability in Allegra’s unzipFile method, allowing authenticated remote attackers to execute arbitrary code in the context of the LOCAL SERVICE account. The flaw stems from improper validation of user-supplied paths during file operations, enabling an attacker to write malicious files outside the intended extraction directory. With a CVSS score of 7.2, this vulnerability poses a significant risk to affected Allegra installations, especially in environments where authentication is weak or compromised. No public proof-of-concept or patch is currently available, but the vulnerability is confirmed by ZDI (ZDI-CAN-23453).

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects the Allegra proprietary application, which is typically deployed as a standalone service.

CVSS Breakdown & Threat Level

• CVSS Score: 7.2 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: Low (Authentication required)
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High

Threat Level: High. Exploitation requires authentication but can lead to full system compromise under the LOCAL SERVICE account, which has elevated privileges on Windows systems.

Deep Dive & Mechanics

The vulnerability resides in the unzipFile method of Allegra. This method is designed to extract ZIP archives to a specified directory. However, it fails to validate or sanitize the paths contained within the ZIP file. An attacker can craft a ZIP archive containing files with directory traversal sequences (e.g., ../../malicious.dll) in their filenames. When Allegra processes this archive, it writes the files to arbitrary locations on the filesystem, bypassing the intended extraction directory.

Key Technical Details:

• Root Cause: Lack of path validation in unzipFile.
• Exploitation Prerequisites: Valid authentication credentials for the Allegra application.
• Impact: Arbitrary file write, leading to remote code execution as LOCAL SERVICE.
• Attack Vector: Remote, via network.
• Authentication Required: Yes.

Vulnerable vs. Patched Code

Since no official patch is available, the following illustrates the vulnerable pattern and a hypothetical fix.

Vulnerable Code (Conceptual):

public void unzipFile(String zipPath, String destDir) {
    ZipInputStream zis = new ZipInputStream(new FileInputStream(zipPath));
    ZipEntry entry;
    while ((entry = zis.getNextEntry()) != null) {
        String entryName = entry.getName();
        File outputFile = new File(destDir, entryName); // No path validation
        // Write entry to outputFile
    }
}

Patched Code (Conceptual):

public void unzipFile(String zipPath, String destDir) {
    ZipInputStream zis = new ZipInputStream(new FileInputStream(zipPath));
    ZipEntry entry;
    while ((entry = zis.getNextEntry()) != null) {
        String entryName = entry.getName();
        // Validate and sanitize path
        File outputFile = new File(destDir, entryName);
        String canonicalDest = new File(destDir).getCanonicalPath();
        String canonicalOutput = outputFile.getCanonicalPath();
        if (!canonicalOutput.startsWith(canonicalDest + File.separator)) {
            throw new SecurityException("Path traversal detected");
        }
        // Write entry to outputFile
    }
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Valid credentials for Allegra.
• Network access to the Allegra service.

Steps:

1. Create a malicious ZIP archive containing a file with a traversal path, e.g., ../../Windows/System32/malicious.dll.
2. Authenticate to Allegra and use the unzipFile functionality to upload and extract the archive.
3. The malicious file is written to the target directory (e.g., C:\Windows\System32\).
4. Trigger execution of the malicious file (e.g., via a scheduled task or service restart).

Example ZIP Creation (Python):

import zipfile

with zipfile.ZipFile('exploit.zip', 'w') as zf:
    zf.writestr('../../Windows/System32/malicious.dll', b'<payload>')

Blue Team

Detection:

• Monitor for unusual file writes to system directories (e.g., C:\Windows\System32\) from the Allegra process.
• Alert on ZIP files containing path traversal sequences in filenames.
• Review authentication logs for suspicious uploads from non-admin accounts.

Mitigation:

• Implement strict input validation on ZIP file contents.
• Use a sandboxed extraction process with restricted file system permissions.
• Apply the principle of least privilege to the Allegra service account.

Indicators of Compromise (IOCs)

• File Artifacts:
  • Unexpected DLLs or executables in C:\Windows\System32\ or C:\Program Files\Allegra\ with recent timestamps.
  • ZIP files with traversal sequences in filenames (e.g., ../../).
• Network Indicators:
  • Connections to Allegra from IPs with a history of file uploads.
• Process Indicators:
  • Allegra process (allegra.exe) writing to system directories.
• Log Entries:
  • Event ID 4663 (Windows) for file writes to protected directories by the Allegra service account.

Detection Engineering

YARA Rule

rule CVE_2024_5581_Allegra_Traversal {
    meta:
        description = "Detects ZIP files with path traversal sequences targeting Allegra"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-5581"
    strings:
        $traversal = /\.\.\/|\.\.\\/
    condition:
        $traversal and (uint32(0) == 0x04034b50) // ZIP local file header signature
}

Sigma Rule

title: CVE-2024-5581 Allegra Directory Traversal
id: 8a9b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects file writes to system directories by Allegra process
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2024-5581
logsource:
    category: file_event
    product: windows
detection:
    selection:
        Image|endswith: '\allegra.exe'
        TargetFilename|startswith:
            - 'C:\Windows\System32\'
            - 'C:\Windows\SysWOW64\'
    condition: selection
falsepositives:
    - Legitimate updates or patches
level: high

Suricata Rule

alert tcp any any -> any 80 (msg:"CVE-2024-5581 Allegra Directory Traversal Attempt"; flow:to_server,established; content:"POST"; http_method; content:"unzipFile"; http_uri; content:"../../"; within:100; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the unzipFile functionality if not essential, or restrict access to trusted users only.
2. Implement a Web Application Firewall (WAF) rule to block ZIP uploads containing path traversal patterns.
3. Monitor logs for exploitation attempts (see IOCs and Detection Engineering).

Long-Term Fix:

• Apply a vendor patch when available.
• Upgrade to a patched version of Allegra.
• Conduct a security review of all file handling functions.

Workaround:

• Use a custom script to validate ZIP contents before processing, rejecting any entries with ../ or ..\ sequences.

Valters IT Signature: This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters.it.