Summary

Backpack\CRUD\Stats::makeCurlRequest builds a shell command using unescaped input that originates from the HTTP Host header, then passes it to exec(). A specially crafted Host header can break out of the shell argument and cause the server to execute arbitrary OS commands as the web user.

The vulnerable code path is reached from BackpackServiceProvider::boot() on every HTTP request in production when exec() and curl are available. A 1-in-100 random gate is the only guard — an attacker can reliably trigger it by retrying.

Severity

High — CVSS 8.1
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Complexity is rated High because default nginx and Apache configurations typically strip or reject malformed Host headers before they reach PHP, and exec() is often disabled for web processes in hardened environments. Both mitigations must be absent for exploitation.

Impact

A successful exploit yields OS command execution as the web server user (www-data, nginx, etc.), giving an unauthenticated attacker access to environment secrets (APP_KEY, database credentials, API keys in .env), the filesystem, and any service the server can reach.

Fix

makeCurlRequest was replaced with the Guzzle-based path already present in the codebase, eliminating the shell-command construction entirely. Upgrade to a patched release immediately.

Affected versions

Credits

Reported by Vishal Shukla (@shukla304) via sechub.dev AI Agent.