CVE-2026-33690: WWBN AVideo Auth Bypass Vulnerability

CVE-2026-33690 Overview

WWBN AVideo, an open source video platform, contains an IP address spoofing vulnerability in versions up to and including 26.0. The getRealIpAddr() function in objects/functions.php trusts user-controlled HTTP headers to determine the client's IP address, allowing attackers to spoof their IP address by sending forged headers. This vulnerability enables bypassing IP-based access controls and circumventing audit logging mechanisms.

Critical Impact

Attackers can bypass IP-based access controls and evade audit logging by spoofing their IP address through forged HTTP headers, potentially enabling unauthorized access and making forensic investigation difficult.

Affected Products

• WWBN AVideo versions up to and including 26.0
• AVideo installations using IP-based access controls
• AVideo deployments relying on IP-based audit logging

Discovery Timeline

• 2026-03-23 - CVE-2026-33690 published to NVD
• 2026-03-25 - Last updated in NVD database

Technical Details for CVE-2026-33690

Vulnerability Analysis

This vulnerability stems from improper trust of user-controlled HTTP headers for IP address determination (CWE-348: Use of Less Trusted Source). The getRealIpAddr() function in objects/functions.php accepts client-supplied HTTP headers like X-Forwarded-For, X-Real-IP, or similar headers without proper validation, allowing attackers to inject arbitrary IP addresses into the application's request handling logic.

When a web application sits behind a reverse proxy or load balancer, it legitimately needs to trust forwarded headers to determine the original client IP. However, when the application fails to validate that these headers originate from a trusted proxy, any client can inject spoofed values directly. This breaks the chain of trust that IP-based security controls depend upon.

Root Cause

The root cause is the getRealIpAddr() function blindly trusting HTTP headers that can be arbitrarily set by clients. The function did not implement proper validation to ensure IP addresses were legitimate or that forwarded headers came from trusted sources. The vulnerable implementation lacked:

1. Validation that the IP address format is legitimate using proper filters
2. Checks to determine if the source IP is from a trusted proxy before accepting forwarded headers
3. Proper sanitization and verification of the REMOTE_ADDR server variable

Attack Vector

The attack is network-accessible and requires no authentication or user interaction. An attacker can exploit this vulnerability by crafting HTTP requests with forged headers such as X-Forwarded-For containing any arbitrary IP address. This allows:

• Bypassing IP-based allowlists or blocklists configured for administrative functions
• Evading geographic access restrictions
• Circumventing rate limiting based on IP addresses
• Poisoning audit logs with false IP addresses to hinder forensic investigation
• Potentially accessing content restricted to specific IP ranges

// Security patch in objects/functions.php
// Source: https://github.com/WWBN/AVideo/commit/1a1df6a9377e5cc67d1d0ac8ef571f7abbffbc6c

     return ($recomended_size <= $max_size);
 }
 
-function getRealIpAddr()
+function getRemoteAddrFromServerArray($server)
 {
-    $ip = "127.0.0.1";
+    if (empty($server['REMOTE_ADDR'])) {
+        return '';
+    }
 
-    if (isCommandLineInterface()) {
-        return $ip;
+    $remoteAddr = trim($server['REMOTE_ADDR']);
+    if (!filter_var($remoteAddr, FILTER_VALIDATE_IP)) {
+        return '';
+    }
+
+    return $remoteAddr;
+}
+
+function isPrivateOrLoopbackIP($ip)
+{
+    if (!filter_var($ip, FILTER_VALIDATE_IP)) {
+        return false;
     }
 
+    return !filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE);
+}
+

The patch introduces proper IP validation using PHP's filter_var() with FILTER_VALIDATE_IP and adds helper functions to distinguish between private/loopback addresses and public addresses, enabling proper trust decisions.

Detection Methods for CVE-2026-33690

Indicators of Compromise

• Unusual or inconsistent IP addresses appearing in access logs compared to network-level logs
• Requests from internal/private IP ranges (10.x.x.x, 192.168.x.x, 172.16-31.x.x) that should not be externally accessible
• Sudden access from IP addresses that bypass geographic or organizational restrictions
• Multiple requests with varying X-Forwarded-For headers from the same source connection

Detection Strategies

• Compare application-level IP logs against web server access logs and network firewall logs to identify discrepancies
• Monitor for HTTP requests containing suspicious X-Forwarded-For, X-Real-IP, or X-Client-IP headers from non-proxy sources
• Implement log correlation rules to detect when claimed IPs don't match actual connection source IPs
• Alert on administrative access from IP addresses not in the expected allowlist

Monitoring Recommendations

• Enable detailed HTTP header logging at the web server level to capture all forwarded IP headers
• Deploy network-level monitoring to correlate actual source IPs with application-reported IPs
• Implement real-time alerting for IP-based access control violations or unusual access patterns
• Review audit logs periodically for inconsistencies in IP address reporting

How to Mitigate CVE-2026-33690

Immediate Actions Required

• Update WWBN AVideo to a version containing commit 1a1df6a9377e5cc67d1d0ac8ef571f7abbffbc6c
• Review any IP-based access controls and consider temporary enforcement at the network/firewall level
• Audit recent access logs for potential exploitation attempts by comparing with network-level logs
• If running behind a reverse proxy, ensure the proxy is configured to sanitize incoming forwarded headers

Patch Information

The vulnerability has been patched in commit 1a1df6a9377e5cc67d1d0ac8ef571f7abbffbc6c. The fix refactors the IP address retrieval functions to implement proper validation using PHP's filter_var() with FILTER_VALIDATE_IP. The new implementation properly validates IP addresses and distinguishes between private/loopback ranges and public addresses before trusting forwarded headers.

For detailed patch information, see the GitHub Commit Details and the GitHub Security Advisory GHSA-8p2x-5cpm-qrqw.

Workarounds

• Configure your reverse proxy or load balancer to strip or overwrite X-Forwarded-For and similar headers from incoming client requests before adding legitimate values
• Implement IP-based access controls at the network firewall level rather than relying on application-level IP detection
• Use additional authentication mechanisms beyond IP-based restrictions for sensitive functionality
• Deploy a Web Application Firewall (WAF) to filter requests with suspicious forwarded IP headers

# Nginx configuration example to sanitize forwarded headers
# Only trust X-Forwarded-For from known proxy IPs

set_real_ip_from 10.0.0.0/8;
set_real_ip_from 172.16.0.0/12;
set_real_ip_from 192.168.0.0/16;
real_ip_header X-Forwarded-For;
real_ip_recursive on;

# Alternatively, completely clear untrusted headers
proxy_set_header X-Forwarded-For $remote_addr;