CVE-2026-34740 Overview
CVE-2026-34740 is a stored Server-Side Request Forgery (SSRF) vulnerability discovered in WWBN AVideo, an open source video platform. The vulnerability exists in the Electronic Program Guide (EPG) link feature, which allows authenticated users with upload permissions to store arbitrary URLs that the server fetches on every EPG page visit. The URL validation relies solely on PHP's FILTER_VALIDATE_URL, which accepts internal network addresses, and critically fails to utilize the platform's existing isSSRFSafeURL() function designed specifically to prevent SSRF attacks.
Critical Impact
Authenticated attackers can leverage this stored SSRF to scan internal networks, access cloud metadata services (such as AWS IMDSv1 at 169.254.169.254), and interact with internal services that should not be externally accessible.
Affected Products
- WWBN AVideo versions 26.0 and prior
- All AVideo deployments with EPG functionality enabled
- Instances where users have upload permissions
Discovery Timeline
- 2026-03-31 - CVE CVE-2026-34740 published to NVD
- 2026-04-01 - Last updated in NVD database
Technical Details for CVE-2026-34740
Vulnerability Analysis
The vulnerability stems from inadequate URL validation in the EPG link handling code path. When authenticated users with upload permissions submit EPG links, the application validates URLs using only PHP's native FILTER_VALIDATE_URL function. This filter accepts syntactically valid URLs but does not restrict access to internal network ranges such as 127.0.0.1, 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, or cloud metadata endpoints.
The security impact is compounded by the stored nature of the vulnerability—the malicious URL persists in the database and triggers server-side requests every time any user visits the EPG page, allowing for repeated exploitation without further attacker interaction.
Root Cause
The root cause is a missing security control in the EPG URL processing code path. WWBN AVideo includes a dedicated isSSRFSafeURL() function specifically designed to prevent SSRF attacks by validating that URLs do not point to internal resources. However, this function is not invoked when processing EPG links, creating an inconsistent security posture where some URL inputs are properly validated while others are not.
This represents a classic case of security control bypass through an alternative code path—the protection exists but is not uniformly applied across all URL-fetching operations.
Attack Vector
The attack requires network access and low privileges (authenticated user with upload permissions). An attacker can exploit this vulnerability by:
- Authenticating to the AVideo platform with an account that has upload permissions
- Navigating to the EPG configuration interface
- Submitting a malicious URL pointing to internal resources (e.g., http://169.254.169.254/latest/meta-data/ for AWS metadata or http://192.168.1.1/admin for internal services)
- The malicious URL is stored in the database
- When any user visits the EPG page, the server fetches the attacker-specified URL and may expose the response or perform actions against internal services
The vulnerability mechanism centers on the server-side request being made with the application server's network context, bypassing firewall rules that would normally prevent external users from accessing internal resources. For detailed technical information, refer to the GitHub Security Advisory.
Detection Methods for CVE-2026-34740
Indicators of Compromise
- Unusual outbound HTTP requests from the AVideo server to internal IP ranges (10.x.x.x, 172.16.x.x, 192.168.x.x, 127.0.0.1)
- Requests to cloud metadata endpoints (169.254.169.254) originating from the application server
- EPG link entries in the database containing internal network addresses or localhost references
- Failed connection attempts or timeouts to internal services logged by the web server
Detection Strategies
- Implement network monitoring to detect outbound connections from the AVideo server to RFC 1918 private address ranges
- Review web server access logs for requests to internal IP addresses or cloud metadata services
- Audit the database for EPG link entries containing suspicious URLs pointing to internal resources
- Deploy Web Application Firewall (WAF) rules to detect and block SSRF patterns in submitted URLs
Monitoring Recommendations
- Enable detailed logging for all URL fetch operations performed by the AVideo application
- Configure alerts for any outbound connections from the application server to internal network segments
- Implement DNS query logging to detect resolution of internal hostnames by the application
- Monitor for unusual response sizes or timings that may indicate successful internal resource access
How to Mitigate CVE-2026-34740
Immediate Actions Required
- Restrict EPG functionality to trusted administrators only until a patch is available
- Implement network-level egress filtering to prevent the AVideo server from accessing internal resources
- Review existing EPG entries for malicious URLs and remove any pointing to internal addresses
- Consider disabling the EPG feature entirely if not critical to operations
Patch Information
At time of publication, there are no publicly available patches for this vulnerability. Monitor the GitHub Security Advisory for updates on official fixes. The recommended remediation would involve modifying the EPG URL handling code to call the existing isSSRFSafeURL() function before storing or fetching any user-supplied URLs.
Workarounds
- Implement Web Application Firewall rules to block URL submissions containing internal IP addresses or cloud metadata endpoints
- Apply network segmentation to isolate the AVideo server from sensitive internal resources
- Use egress proxy filtering to prevent direct outbound connections to internal network ranges
- Limit upload permissions to only trusted users who require this functionality
# Example iptables rules to restrict outbound connections to internal ranges
# Apply on the AVideo server
# Block connections to private network ranges
iptables -A OUTPUT -d 10.0.0.0/8 -j DROP
iptables -A OUTPUT -d 172.16.0.0/12 -j DROP
iptables -A OUTPUT -d 192.168.0.0/16 -j DROP
iptables -A OUTPUT -d 127.0.0.0/8 -j DROP
# Block AWS metadata endpoint
iptables -A OUTPUT -d 169.254.169.254 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
