CVE-2025-10410: Rems Link Status Checker SSRF Vulnerability

CVE-2025-10410 Overview

A Server-Side Request Forgery (SSRF) vulnerability has been identified in SourceCodester Link Status Checker version 1.0. This vulnerability exists in the index.php file where improper handling of the proxy argument allows attackers to manipulate server-side requests. The flaw enables remote attackers to forge requests from the vulnerable server, potentially accessing internal resources, bypassing access controls, or scanning internal network infrastructure.

Critical Impact

Remote attackers can exploit this SSRF vulnerability to make arbitrary server-side requests, potentially accessing internal services, exfiltrating sensitive data, or pivoting to attack internal infrastructure.

Affected Products

• SourceCodester Link Status Checker 1.0
• REMS Link Status Checker 1.0

Discovery Timeline

• 2025-09-14 - CVE-2025-10410 published to NVD
• 2025-09-18 - Last updated in NVD database

Technical Details for CVE-2025-10410

Vulnerability Analysis

This Server-Side Request Forgery vulnerability occurs due to insufficient validation of user-supplied input in the proxy parameter within index.php. The Link Status Checker application is designed to verify the availability of URLs, but the proxy functionality fails to properly sanitize or restrict the target of outbound requests.

When an attacker supplies a crafted value to the proxy argument, the server-side application processes the request without adequate validation. This allows the attacker to redirect server-side HTTP requests to arbitrary destinations, including internal network resources that would otherwise be inaccessible from external networks.

The vulnerability is classified under CWE-918 (Server-Side Request Forgery), which describes scenarios where a web application fetches remote resources based on user-supplied input without proper validation of the destination URL.

Root Cause

The root cause of this vulnerability stems from improper input validation in the index.php file. The application accepts the proxy parameter and uses it to construct server-side HTTP requests without implementing adequate security controls such as:

• URL scheme validation (restricting to HTTP/HTTPS only)
• Hostname validation against allowlists
• Private IP address filtering
• DNS rebinding protections

This allows attackers to specify arbitrary URLs including internal IP addresses, localhost references, and cloud metadata endpoints.

Attack Vector

The attack can be initiated remotely over the network by authenticated users with low privileges. An attacker can exploit this vulnerability by sending crafted HTTP requests to index.php with a malicious proxy parameter value. Potential attack scenarios include:

• Accessing internal services on localhost (127.0.0.1)
• Scanning internal network infrastructure
• Retrieving cloud instance metadata from endpoints like http://169.254.169.254/
• Bypassing firewall restrictions by making requests appear to originate from the trusted server

The exploit has been publicly disclosed, increasing the risk of active exploitation. For technical details, see the GitHub PoC Repository and VulDB entry #323844.

Detection Methods for CVE-2025-10410

Indicators of Compromise

• Unusual outbound HTTP requests from the web server to internal IP addresses (10.x.x.x, 172.16.x.x, 192.168.x.x)
• Requests to cloud metadata endpoints (169.254.169.254) originating from the application server
• Abnormal traffic patterns from index.php to non-standard ports or services
• Log entries showing requests to localhost or loopback addresses from external user sessions

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block SSRF patterns in the proxy parameter
• Monitor application logs for requests containing internal IP addresses or localhost references
• Deploy network monitoring to identify unusual outbound connections from the web server to internal resources
• Configure intrusion detection systems (IDS) to alert on SSRF attack signatures targeting index.php

Monitoring Recommendations

• Enable detailed logging for all requests to index.php including full parameter values
• Set up alerts for outbound connections from the application server to RFC 1918 private IP ranges
• Monitor DNS queries from the web server for potential DNS rebinding attempts
• Review access logs regularly for patterns consistent with SSRF reconnaissance activities

How to Mitigate CVE-2025-10410

Immediate Actions Required

• Disable or remove the Link Status Checker application if not actively required
• Implement network segmentation to restrict the web server's ability to access internal resources
• Deploy a web application firewall with SSRF-specific rules to filter malicious proxy parameter values
• Apply input validation at the application level to restrict allowed URL schemes and destinations

Patch Information

No official vendor patch has been released at this time. Users should check SourceCodester for security updates. Until a patch is available, implementing the workarounds below is strongly recommended.

Additional technical details are available through the VulDB CTI entry and VulDB submission #646911.

Workarounds

• Implement URL allowlisting to restrict the proxy parameter to approved external domains only
• Block outbound requests to private IP ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 127.0.0.0/8) at the network level
• Use a dedicated proxy server with strict egress filtering for all application outbound requests
• Consider removing or commenting out the proxy functionality in index.php until a patch is available

# Example iptables rules to block SSRF to internal networks
# Apply on the web server hosting Link Status Checker

# Block outbound to private IP ranges from web server
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
iptables -A OUTPUT -d 169.254.169.254 -j DROP