CVE-2026-4831: Kalcaddle KodBox Auth Bypass Vulnerability

CVE-2026-4831 Overview

A security flaw has been discovered in kalcaddle kodbox version 1.64. The vulnerability affects the can function within the file /workspace/source-code/app/controller/explorer/auth.class.php of the Password-protected Share Handler component. This improper authentication vulnerability allows attackers to manipulate authentication processes, potentially bypassing password protection on shared resources.

Critical Impact

This authentication bypass vulnerability could allow unauthorized access to password-protected shared files and folders in kodbox deployments, compromising data confidentiality.

Affected Products

• kalcaddle kodbox version 1.64
• Password-protected Share Handler component
• /workspace/source-code/app/controller/explorer/auth.class.php

Discovery Timeline

• 2026-03-26 - CVE-2026-4831 published to NVD
• 2026-03-26 - Last updated in NVD database

Technical Details for CVE-2026-4831

Vulnerability Analysis

This vulnerability is classified as CWE-287 (Improper Authentication), indicating a fundamental flaw in how the kodbox application validates user authentication for password-protected shares. The affected can function in the auth.class.php file fails to properly verify authentication credentials, allowing attackers to bypass password protection mechanisms.

The attack can be executed remotely over the network, though the complexity is considered high and exploitation is difficult. The vendor (kalcaddle) was contacted about this disclosure but did not respond, leaving affected users without an official patch.

Root Cause

The root cause lies in improper authentication validation within the Password-protected Share Handler component. The can function in auth.class.php does not adequately verify that a user has provided valid credentials before granting access to protected resources. This implementation oversight allows authentication bypass under specific conditions.

Attack Vector

The vulnerability is exploitable remotely via the network. An attacker can target the Password-protected Share Handler component by manipulating authentication requests to the affected can function. While the attack complexity is high and requires specific conditions to be met, a successful exploit could grant unauthorized access to password-protected shared content.

The exploit has been publicly disclosed and may be used for attacks. Technical details are available through the VulnPlus Note Sharing resource.

Detection Methods for CVE-2026-4831

Indicators of Compromise

• Unusual access patterns to password-protected shared resources without corresponding successful authentication events
• Multiple failed authentication attempts followed by successful resource access without valid credentials
• Anomalous requests targeting /app/controller/explorer/auth.class.php endpoints

Detection Strategies

• Monitor web server access logs for suspicious requests to the auth.class.php file and related share handler endpoints
• Implement application-level logging to track authentication attempts and access to protected shares
• Deploy web application firewall (WAF) rules to detect authentication bypass attempts
• Review audit logs for unauthorized access to password-protected resources

Monitoring Recommendations

• Enable verbose logging for the kodbox application, particularly for authentication events
• Set up alerts for access to protected resources without corresponding authentication success events
• Monitor for exploitation attempts using signatures based on known attack patterns from the public disclosure

How to Mitigate CVE-2026-4831

Immediate Actions Required

• Restrict network access to kodbox instances to trusted networks only until a patch is available
• Implement additional authentication layers (such as VPN or reverse proxy authentication) for accessing shared resources
• Review and audit all password-protected shares for unauthorized access
• Consider temporarily disabling the password-protected share feature if not critical to operations

Patch Information

No official patch is currently available from the vendor. According to the vulnerability disclosure, kalcaddle was contacted about this issue but did not respond. Users should monitor the vendor's official channels for future security updates.

For additional technical details and ongoing updates, refer to:

• VulDB Entry #353128
• VulDB CTI Information

Workarounds

• Implement network-level access controls to limit exposure of kodbox instances to trusted IP ranges
• Add an additional authentication layer via a reverse proxy (e.g., nginx basic auth or OAuth)
• Disable password-protected sharing functionality until a vendor patch becomes available
• Migrate sensitive shared content to alternative secure file sharing solutions

# Example: Restrict access to kodbox at the web server level (nginx)
location /app/controller/explorer/ {
    # Restrict to trusted IP ranges only
    allow 192.168.1.0/24;
    allow 10.0.0.0/8;
    deny all;
}