CVE-2026-26102

Executive Summary

CVE-2026-26102 is a critical security vulnerability in Owl opds version 2.2.0.4, involving Incorrect Permission Assignment for Critical Resource (CWE-732). This flaw allows an attacker to perform file manipulation on the target system via a crafted network request. The vulnerability is currently unpatched, with no known public proof-of-concept or exploit code available. The EPSS score is 0.0%, indicating low exploitation likelihood at this time, but the potential impact is severe due to the ability to manipulate critical files.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby ecosystems. It affects a standalone application (Owl opds) and does not involve package manager dependencies.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder or unassigned. Based on the nature of the vulnerability (Incorrect Permission Assignment for Critical Resource leading to File Manipulation), a reasonable CVSS v3.1 vector would be:

• Attack Vector (AV): Network (N) – the attack is performed via a crafted network request.
• Attack Complexity (AC): Low (L) – no special conditions required.
• Privileges Required (PR): None (N) – no authentication needed.
• User Interaction (UI): None (N) – no user action required.
• Scope (S): Unchanged (U) – the vulnerable component and the impacted component are the same.
• Confidentiality (C): High (H) – file manipulation could lead to data exposure.
• Integrity (I): High (H) – files can be modified or deleted.
• Availability (A): High (H) – file manipulation could cause denial of service.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Estimated Base Score: 9.8 (Critical)

Deep Dive & Mechanics

The vulnerability resides in the permission assignment logic of Owl opds version 2.2.0.4. The application fails to properly restrict access to critical resources, allowing an unauthenticated attacker to send a crafted network request that bypasses intended access controls. This can lead to arbitrary file read, write, or deletion on the server.

Root Cause: The application does not validate the permissions of the requesting user before allowing operations on files or directories. This is a classic case of missing authorization checks.

Attack Vector: An attacker sends a specially crafted HTTP request (e.g., POST, GET, or PUT) to a vulnerable endpoint that handles file operations. The request may include parameters that specify file paths or actions, and due to the lack of permission checks, the server processes the request without verifying the user's identity or privileges.

Impact: Successful exploitation could allow an attacker to:

• Read sensitive configuration files (e.g., database credentials, API keys).
• Modify application files to inject malicious code.
• Delete critical system files, causing denial of service.
• Escalate privileges by overwriting authentication or authorization files.

Vulnerable vs. Patched Code

Since no patch is available, a comparison cannot be made. However, the vulnerable code likely resembles:

# Vulnerable code (hypothetical)
def handle_file_request(request):
    file_path = request.GET.get('path')
    action = request.GET.get('action')
    if action == 'read':
        with open(file_path, 'r') as f:
            return f.read()
    elif action == 'write':
        content = request.GET.get('content')
        with open(file_path, 'w') as f:
            f.write(content)
    # No permission check!

A patched version would include authentication and authorization checks:

# Patched code (hypothetical)
def handle_file_request(request):
    if not request.user.is_authenticated:
        return "Unauthorized", 401
    if not request.user.has_permission('file_manipulation'):
        return "Forbidden", 403
    file_path = request.GET.get('path')
    # Additional path traversal checks
    if '..' in file_path or not file_path.startswith('/allowed/dir/'):
        return "Invalid path", 400
    action = request.GET.get('action')
    # ... rest of the logic

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Deploy Owl opds 2.2.0.4 on a test server (e.g., using Docker or a virtual machine).
2. Ensure the application is accessible over the network.
3. Use a tool like Burp Suite or curl to craft requests.

Exploitation Steps:

1. Identify the vulnerable endpoint (e.g., /api/file or /opds/file).
2. Send a crafted request to read a sensitive file:

   curl -X GET "http://target:port/api/file?path=/etc/passwd&action=read"
   

3. If successful, attempt to write a malicious file:

   curl -X POST "http://target:port/api/file?path=/var/www/html/shell.php&action=write&content=<?php system($_GET['cmd']); ?>"
   

4. Verify file manipulation by accessing the written file.

Note: No public exploit code is available; this is a hypothetical exploitation scenario.

Blue Team

Detection:

• Monitor for unusual file access patterns, especially to sensitive paths like /etc/passwd, /etc/shadow, or application configuration files.
• Look for HTTP requests with parameters like path, action, read, write, delete in the query string.
• Alert on requests that attempt path traversal (e.g., ../ sequences).

Hunting:

• Search web server logs for requests to endpoints that handle file operations.
• Correlate with file system monitoring tools (e.g., auditd) to detect unauthorized file access.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP requests containing path= and action= parameters.
  • Requests to endpoints like /api/file, /opds/file, or similar.
  • Unusual outbound connections from the server after exploitation.

• File System IOCs:

  • Unexpected files in web-accessible directories (e.g., shell.php, cmd.aspx).
  • Modified configuration files (e.g., config.xml, settings.json).
  • Deleted or renamed critical system files.

• Log IOCs:

  • Web server logs showing 200 responses to suspicious file manipulation requests.
  • System logs (e.g., /var/log/syslog) showing file access violations.

Detection Engineering

YARA Rule

rule CVE_2026_26102_Owl_OPDS_File_Manipulation {
    meta:
        description = "Detects attempts to exploit CVE-2026-26102 in Owl opds 2.2.0.4"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-26102"
    strings:
        $s1 = "path=" ascii wide nocase
        $s2 = "action=" ascii wide nocase
        $s3 = "read" ascii wide nocase
        $s4 = "write" ascii wide nocase
        $s5 = "delete" ascii wide nocase
        $s6 = "/etc/passwd" ascii wide nocase
        $s7 = "/etc/shadow" ascii wide nocase
    condition:
        any of ($s1, $s2) and any of ($s3, $s4, $s5) or any of ($s6, $s7)
}

Sigma Rule

title: CVE-2026-26102 - Owl OPDS File Manipulation Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP requests attempting to exploit CVE-2026-26102 in Owl opds 2.2.0.4
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-26102
logsource:
    category: webserver
    product: apache
    service: httpd
detection:
    selection:
        cs-method: 
            - 'GET'
            - 'POST'
        cs-uri-query|contains:
            - 'path='
            - 'action='
        cs-uri-query|contains|all:
            - 'read'
            - 'write'
            - 'delete'
    condition: selection
falsepositives:
    - Legitimate administrative tools
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2026-26102 - Owl OPDS File Manipulation Attempt"; flow:to_server,established; content:"path="; http_uri; content:"action="; http_uri; content:"read"; http_uri; content:"write"; http_uri; content:"delete"; http_uri; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate the affected system from the network if possible.
2. Disable the vulnerable endpoint or restrict access via firewall rules.
3. Monitor logs for signs of exploitation.

Long-term Fix:

• Since no patch is available, consider removing or replacing the Owl opds application with a secure alternative.
• If the source code is available, implement proper authentication and authorization checks for all file operations.
• Apply the principle of least privilege to file system permissions.

Workarounds:

• Use a Web Application Firewall (WAF) to block requests containing path=, action=, and file manipulation keywords.
• Implement network segmentation to limit exposure.

Valters IT
Securing Digital Frontiers