CVE-2026-4592: KodBox Authentication Bypass Vulnerability

CVE-2026-4592 Overview

A security vulnerability has been identified in kalcaddle kodbox version 1.64 that allows improper authentication through the Password Login component. This vulnerability affects the loginAfter/tfaVerify function within the file /workspace/source-code/plugins/client/controller/tfa/index.class.php. When exploited, an attacker can bypass authentication mechanisms remotely, though the attack requires high complexity to execute successfully.

Critical Impact

Remote attackers can potentially bypass authentication controls in the two-factor authentication (TFA) verification process, compromising account security and potentially gaining unauthorized access to protected resources.

Affected Products

• kalcaddle kodbox version 1.64

Discovery Timeline

• 2026-03-23 - CVE-2026-4592 published to NVD
• 2026-03-24 - Last updated in NVD database

Technical Details for CVE-2026-4592

Vulnerability Analysis

This vulnerability falls under CWE-287 (Improper Authentication), indicating that the authentication mechanism in kodbox's TFA verification process fails to properly validate user credentials or session state. The vulnerability exists in the password login workflow, specifically in how the system handles post-login authentication and two-factor authentication verification.

The attack is network-based, meaning it can be exploited remotely without requiring local access to the target system. However, the high attack complexity suggests that specific conditions must be met or that the exploitation requires sophisticated techniques to succeed. The exploit has been publicly disclosed, increasing the risk of exploitation attempts despite the complexity involved.

Root Cause

The root cause lies in improper authentication handling within the loginAfter/tfaVerify function in the TFA plugin controller. The vulnerability suggests that the authentication state or token validation during the TFA verification phase does not adequately verify the legitimacy of the authentication request, potentially allowing attackers to manipulate the authentication flow.

Attack Vector

The attack is conducted remotely over the network, targeting the Password Login component of kodbox. An attacker would need to interact with the TFA verification endpoint and manipulate the authentication process. The high complexity rating indicates that successful exploitation likely requires:

• Understanding of the internal authentication state machine
• Potential race conditions or timing-based attacks
• Manipulation of session or authentication tokens during the TFA verification phase

The vulnerability affects confidentiality, integrity, and availability with low impact in each category, suggesting that while exploitation is possible, the immediate damage may be limited to partial information disclosure or authentication bypass for specific operations.

Detection Methods for CVE-2026-4592

Indicators of Compromise

• Anomalous authentication attempts targeting /workspace/source-code/plugins/client/controller/tfa/index.class.php or related TFA endpoints
• Unusual patterns in TFA verification requests, including repeated or malformed requests to the loginAfter/tfaVerify function
• Authentication success logs without corresponding valid TFA completion records
• Unexpected session creation patterns during the login process

Detection Strategies

• Monitor web server access logs for suspicious requests to TFA-related endpoints with unusual parameters or request patterns
• Implement application-level logging to track authentication flow anomalies, particularly in the TFA verification step
• Deploy web application firewall (WAF) rules to detect and block requests attempting to manipulate authentication parameters
• Analyze authentication audit logs for successful logins that bypass expected TFA verification workflows

Monitoring Recommendations

• Enable detailed logging for all authentication-related functions in kodbox, especially the TFA plugin components
• Set up alerts for authentication anomalies such as high-frequency TFA verification attempts from single IP addresses
• Monitor for unauthorized access to resources following suspicious authentication patterns
• Implement rate limiting on the TFA verification endpoint to slow potential exploitation attempts

How to Mitigate CVE-2026-4592

Immediate Actions Required

• Review authentication logs for any evidence of exploitation attempts targeting the TFA verification process
• Consider temporarily restricting access to the kodbox instance to trusted networks if critical data is at risk
• Implement additional access controls at the network level to limit exposure of the vulnerable endpoint
• Monitor for vendor updates or community patches addressing this vulnerability

Patch Information

As of the last update, the vendor (kalcaddle) was contacted about this vulnerability but did not respond. No official patch has been confirmed. Users should monitor the official kodbox repository and VulDB entry for updates regarding patches or recommended mitigations.

Workarounds

• Implement network-level access controls to restrict access to the kodbox login interface to trusted IP addresses only
• Deploy a web application firewall (WAF) with rules to validate and sanitize authentication requests before they reach the application
• Consider disabling the TFA plugin temporarily if the additional security layer is not strictly required in your environment
• Enable enhanced logging and monitoring to detect and respond to exploitation attempts quickly

# Example: Restrict access to kodbox at the web server level (Nginx)
# Add to your server block configuration
location /plugins/client/controller/tfa/ {
    allow 192.168.1.0/24;  # Trusted internal network
    deny all;
    # Additional rate limiting
    limit_req zone=tfa_limit burst=5 nodelay;
}

# Define rate limit zone in http block
# limit_req_zone $binary_remote_addr zone=tfa_limit:10m rate=10r/m;