CVE-2026-5126 Overview
CVE-2026-5126 is a Server-Side Request Forgery (SSRF) vulnerability affecting SourceCodester RSS Feed Parser 1.0. The flaw resides in the application's use of the PHP file_get_contents function, which processes user-supplied URLs without sufficient validation. Remote attackers with low-level privileges can manipulate the input to make the server issue arbitrary outbound HTTP requests. A public exploit has been published, increasing the likelihood of opportunistic abuse. The weakness is classified under CWE-918: Server-Side Request Forgery.
Critical Impact
Attackers can coerce the vulnerable server into issuing requests to internal services, cloud metadata endpoints, or other hosts reachable from the application, enabling reconnaissance and limited data exposure.
Affected Products
- SourceCodester RSS Feed Parser 1.0
- PHP applications that pass untrusted input directly to file_get_contents
- Deployments exposing the parser endpoint to authenticated remote users
Discovery Timeline
- 2026-03-30 - CVE-2026-5126 published to NVD
- 2026-04-29 - Last updated in NVD database
Technical Details for CVE-2026-5126
Vulnerability Analysis
The vulnerability stems from unsafe handling of a URL parameter passed to PHP's file_get_contents function inside SourceCodester RSS Feed Parser 1.0. The application accepts a remote feed URL from the user and fetches its contents server-side without validating the host, scheme, or destination. An attacker can replace the legitimate feed URL with an arbitrary target, causing the server to perform HTTP, HTTPS, file, or other wrapper-supported requests on the attacker's behalf. Because the response or its side effects can sometimes be observed, this enables Blind SSRF and, depending on PHP wrapper configuration, potential local file disclosure through the file:// scheme. For technical context, see the Medium blog on the SSRF vulnerability and the VulDB entry #354158.
Root Cause
The root cause is missing input validation on a URL parameter consumed by file_get_contents. The parser does not enforce an allowlist of schemes, does not resolve and check the destination IP against private or loopback ranges, and does not restrict redirects. Any value the user submits becomes the fetch target.
Attack Vector
Exploitation is remote and requires low-privileged access to the parser endpoint. The attacker submits a crafted URL pointing to internal hosts such as http://127.0.0.1, http://169.254.169.254 (cloud metadata), or other private addresses. The PHP runtime issues the request and the parser processes the response, allowing the attacker to map internal services or trigger unauthenticated internal endpoints.
No verified exploit code is published in the referenced advisories. The vulnerability mechanism is described in prose; refer to the Medium write-up for the researcher's analysis.
Detection Methods for CVE-2026-5126
Indicators of Compromise
- Outbound HTTP requests from the web server to RFC1918 addresses, 127.0.0.1, or 169.254.169.254 originating from the PHP process.
- Web server access logs showing repeated requests to the RSS Feed Parser endpoint with URL parameters pointing to non-feed hosts.
- Unexpected file://, gopher://, or dict:// scheme values appearing in request parameters.
Detection Strategies
- Inspect application logs for parser requests whose URL parameter resolves to internal IP space or cloud metadata services.
- Correlate egress firewall logs with PHP process identifiers to surface server-initiated requests that bypass normal user-driven traffic patterns.
- Apply WAF rules that match SSRF payload patterns such as encoded localhost addresses, IPv6 loopback, and decimal-encoded IPs.
Monitoring Recommendations
- Enable verbose request logging on the parser endpoint, capturing the full URL parameter value.
- Monitor egress traffic from web servers to cloud instance metadata endpoints and alert on any access.
- Track DNS resolution requests originating from the PHP runtime for anomalous internal hostnames.
How to Mitigate CVE-2026-5126
Immediate Actions Required
- Restrict access to the RSS Feed Parser endpoint to trusted users until a fix is applied.
- Block outbound traffic from the web server to internal networks and cloud metadata IPs at the egress firewall.
- Replace file_get_contents calls on user-supplied URLs with a wrapper that enforces scheme and destination allowlists.
Patch Information
No vendor patch is referenced in the available advisories. Operators should treat the project as unmaintained for this issue and apply compensating controls. Monitor the SourceCodester site and VulDB submission #780180 for updates.
Workarounds
- Validate the user-supplied URL against an allowlist of trusted feed hostnames before invoking file_get_contents.
- Force the HTTP scheme and reject file://, phar://, gopher://, and other non-HTTP wrappers.
- Resolve the target hostname and reject any address in private, loopback, link-local, or reserved ranges prior to the request.
- Run the PHP process under a network policy that denies access to internal subnets and cloud metadata endpoints.
# Example egress restriction using iptables to block metadata access
iptables -A OUTPUT -m owner --uid-owner www-data -d 169.254.169.254 -j REJECT
iptables -A OUTPUT -m owner --uid-owner www-data -d 127.0.0.0/8 -j REJECT
iptables -A OUTPUT -m owner --uid-owner www-data -d 10.0.0.0/8 -j REJECT
iptables -A OUTPUT -m owner --uid-owner www-data -d 192.168.0.0/16 -j REJECT
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
