CVE-2026-5126: RSS Feed Parser 1.0 SSRF Vulnerability

CVE-2026-5126 Overview

A Server-Side Request Forgery (SSRF) vulnerability has been identified in SourceCodester RSS Feed Parser 1.0. The vulnerability exists in the file_get_contents function, which fails to properly validate user-supplied URLs before making server-side requests. This allows remote authenticated attackers to manipulate the application into making arbitrary HTTP requests to internal or external resources, potentially exposing sensitive internal services or data.

Critical Impact

Remote attackers can exploit this SSRF vulnerability to access internal network resources, scan internal ports, retrieve sensitive data from internal services, or pivot to attack other systems within the network infrastructure.

Affected Products

• SourceCodester RSS Feed Parser 1.0

Discovery Timeline

• 2026-03-30 - CVE-2026-5126 published to NVD
• 2026-04-01 - Last updated in NVD database

Technical Details for CVE-2026-5126

Vulnerability Analysis

This vulnerability is classified as Server-Side Request Forgery (SSRF) under CWE-918. The RSS Feed Parser application accepts user-supplied URLs to fetch RSS feed content but fails to implement proper validation or filtering of these URLs before passing them to the file_get_contents PHP function.

The lack of input sanitization allows attackers to supply malicious URLs targeting internal network resources, cloud metadata endpoints, or other sensitive services. This can lead to unauthorized access to internal systems, information disclosure, and potential further exploitation of internal services that would normally be inaccessible from external networks.

The vulnerability can be exploited remotely by any authenticated user with access to the RSS feed parsing functionality. An exploit for this vulnerability has been publicly disclosed, increasing the risk of active exploitation.

Root Cause

The root cause of this vulnerability lies in the insecure implementation of the file_get_contents function within the RSS Feed Parser application. The function is called with user-controlled input without proper validation, allowing attackers to specify arbitrary URLs including those targeting internal resources.

PHP's file_get_contents function is capable of fetching content from various protocols including http://, https://, file://, and potentially others depending on PHP configuration. Without proper URL validation and protocol restrictions, this creates a dangerous attack surface.

Attack Vector

The attack is network-based and can be performed remotely. An attacker with low privileges (authenticated access to the application) can exploit this vulnerability without user interaction. The exploitation involves submitting a crafted URL to the RSS feed parsing functionality.

A typical attack scenario involves an attacker providing a malicious URL such as an internal IP address (e.g., http://127.0.0.1:8080/admin), cloud metadata endpoints (e.g., http://169.254.169.254/latest/meta-data/), or internal hostname references to probe and access internal network resources. For detailed technical analysis, refer to the Medium Blog on SSRF Vulnerability.

Detection Methods for CVE-2026-5126

Indicators of Compromise

• Unusual outbound HTTP requests from the web server to internal IP addresses or localhost
• HTTP requests to cloud provider metadata endpoints (e.g., 169.254.169.254)
• Access logs showing requests with internal URLs or private IP ranges in user-supplied parameters
• Network traffic from the web server to unexpected internal services or ports

Detection Strategies

• Monitor web application logs for RSS feed URLs containing internal IP addresses, localhost references, or private network ranges
• Implement network-level monitoring to detect outbound connections from web servers to internal infrastructure
• Deploy Web Application Firewalls (WAF) with SSRF detection rules to block requests containing suspicious URL patterns
• Use SentinelOne Singularity Platform to detect and alert on anomalous network behavior from web application processes

Monitoring Recommendations

• Enable detailed logging for all RSS feed parsing operations, including the URLs being requested
• Configure network security monitoring to alert on web server connections to internal network segments
• Implement egress filtering and monitoring to detect unauthorized outbound connections
• Review application logs regularly for patterns indicating SSRF exploitation attempts

How to Mitigate CVE-2026-5126

Immediate Actions Required

• Restrict or disable the RSS feed parsing functionality until a patch is available
• Implement URL validation to block requests to internal IP addresses and private network ranges
• Configure firewall rules to prevent the web server from making connections to internal services
• Apply network segmentation to limit the impact of potential SSRF attacks

Patch Information

No vendor patch information is currently available for this vulnerability. Users should monitor the SourceCodester website for security updates. Additional vulnerability details can be found at VulDB Vulnerability #354158.

Workarounds

• Implement a URL allowlist that restricts RSS feed sources to known, trusted external domains only
• Configure PHP to disable dangerous URL wrappers by setting allow_url_fopen = Off if RSS functionality is not critical
• Deploy a proxy server that validates and sanitizes all outbound requests from the application
• Use network-level controls to block the web server from accessing internal network resources

# Configuration example - PHP settings to restrict URL functions
# Add to php.ini or .htaccess

# Disable URL wrappers for file functions (may break RSS functionality)
allow_url_fopen = Off
allow_url_include = Off

# If RSS functionality is required, implement network-level restrictions
# Example iptables rule to block internal network access from web server
# iptables -A OUTPUT -m owner --uid-owner www-data -d 10.0.0.0/8 -j DROP
# iptables -A OUTPUT -m owner --uid-owner www-data -d 172.16.0.0/12 -j DROP
# iptables -A OUTPUT -m owner --uid-owner www-data -d 192.168.0.0/16 -j DROP
# iptables -A OUTPUT -m owner --uid-owner www-data -d 127.0.0.0/8 -j DROP
# iptables -A OUTPUT -m owner --uid-owner www-data -d 169.254.169.254 -j DROP