CVE-2026-33432: Roxy-WI Auth Bypass Vulnerability

CVE-2026-33432 Overview

CVE-2026-33432 is a critical LDAP Injection vulnerability in Roxy-WI, a popular web interface for managing Haproxy, Nginx, Apache, and Keepalived servers. When LDAP authentication is enabled, the application constructs an LDAP search filter by directly concatenating user-supplied login credentials into the filter string without proper escaping of LDAP special characters. This allows an unauthenticated attacker to inject LDAP filter metacharacters into the username field, manipulating the search query to return unintended user entries and completely bypassing authentication.

Critical Impact

Unauthenticated attackers can gain full access to the Roxy-WI management interface without knowing any valid credentials, potentially compromising the management of critical infrastructure including load balancers and web servers.

Affected Products

• Roxy-WI versions up to and including 8.2.8.2
• Roxy-WI installations with LDAP authentication enabled
• All deployment environments utilizing LDAP directory services for authentication

Discovery Timeline

• 2026-04-20 - CVE-2026-33432 published to NVD
• 2026-04-21 - Last updated in NVD database

Technical Details for CVE-2026-33432

Vulnerability Analysis

This vulnerability falls under CWE-287 (Improper Authentication) and represents a classic LDAP Injection flaw. The vulnerable code resides in the authentication module at app/modules/roxywi/auth.py. When a user attempts to authenticate via LDAP, Roxy-WI takes the user-supplied username and directly incorporates it into an LDAP search filter without sanitizing or escaping special characters.

LDAP filters use specific metacharacters such as *, (, ), \, and | to construct queries. When these characters are not properly escaped in user input, an attacker can craft malicious usernames that alter the logic of the LDAP query itself. For example, injecting wildcard characters or logical operators can cause the directory server to return different user entries than intended, effectively allowing authentication as any user in the directory.

Root Cause

The root cause is insufficient input validation and the absence of LDAP special character escaping in the authentication flow. The auth.py module performs direct string concatenation when building the LDAP search filter, treating user-controlled input as trusted data. Proper LDAP filter construction requires escaping characters defined in RFC 4515, including parentheses, asterisks, backslashes, and null bytes.

Attack Vector

The attack is network-based and requires no prior authentication or special privileges. An attacker can exploit this vulnerability by:

1. Navigating to the Roxy-WI login page
2. Entering a crafted username containing LDAP metacharacters (such as * or filter expressions like )(uid=*))
3. Submitting any password value
4. The malformed LDAP query returns an unintended user entry, and authentication succeeds

The vulnerability in the authentication module can be examined in the Roxy-WI auth.py source code. The direct concatenation of user input into the LDAP filter without proper escaping allows filter manipulation. For technical details on the exploitation mechanism, refer to the GitHub Security Advisory.

Detection Methods for CVE-2026-33432

Indicators of Compromise

• Authentication logs showing unusual username patterns containing LDAP metacharacters such as *, (, ), |, or \
• Multiple successful authentications from the same IP address with varying or malformed usernames
• LDAP server logs indicating unusual or malformed search queries
• Access to Roxy-WI administrative functions from unexpected user accounts or IP addresses

Detection Strategies

• Monitor authentication logs for usernames containing LDAP special characters including asterisks, parentheses, backslashes, and pipe characters
• Implement Web Application Firewall (WAF) rules to detect and block LDAP injection patterns in POST parameters
• Review LDAP server audit logs for search filter anomalies or queries returning unexpected results
• Deploy SentinelOne Singularity to detect post-exploitation activity and lateral movement following authentication bypass

Monitoring Recommendations

• Enable verbose logging on the LDAP directory server to capture complete search filter queries
• Configure alerting for authentication events with usernames matching known LDAP injection patterns
• Monitor network traffic to the Roxy-WI application for suspicious login attempts
• Implement rate limiting on authentication endpoints to slow down brute-force injection attempts

How to Mitigate CVE-2026-33432

Immediate Actions Required

• Disable LDAP authentication in Roxy-WI and switch to local authentication or an alternative identity provider until a patch is available
• Restrict network access to the Roxy-WI management interface using firewall rules or VPN requirements
• Implement a reverse proxy with WAF capabilities to filter malicious input before it reaches the application
• Audit existing user sessions and invalidate any potentially compromised sessions
• Review access logs for signs of exploitation and investigate any suspicious authentication activity

Patch Information

As of the publication date, no official patch is available for this vulnerability. The vendor has not yet released a security update addressing this LDAP injection flaw. Organizations should monitor the Roxy-WI GitHub repository and the GitHub Security Advisory for patch announcements.

Workarounds

• Disable LDAP authentication entirely and use local authentication methods until a patch is released
• Place Roxy-WI behind a VPN or restrict access to trusted IP addresses only
• Implement a reverse proxy with input validation to filter LDAP metacharacters from the username field
• Enable multi-factor authentication at the network level as an additional security layer

# Example: Restrict access to Roxy-WI using iptables (adjust IPs as needed)
# Block all traffic to Roxy-WI port except from trusted management IPs
iptables -A INPUT -p tcp --dport 443 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP

# Alternatively, disable LDAP in Roxy-WI configuration
# Edit roxy-wi configuration to use local authentication instead of LDAP