Executive brief
The Apache HTTP Server is a widely used web server for hosting websites and applications. A vulnerability in its FTP proxy module allows a malicious or compromised backend FTP server to trigger an infinite loop on the web server. This can lead to a denial-of-service (DoS) condition, making the web server unresponsive to legitimate users and potentially impacting business operations.
Technical details
A Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability exists in the mod_proxy_ftp module of Apache HTTP Server. The flaw is located in the proxy_ftp_handler function and is triggered when the server interacts with an attacker-controlled or malicious backend FTP server. By sending a specifically crafted response, the backend server can cause the Apache process to enter an infinite loop, consuming CPU resources and leading to a denial-of-service (DoS). The issue is fixed in version 2.4.68.
Affected products
- Apache HTTP Server 2.4.0 through 2.4.67
Timeline
- 2026-04-27: disclosed: Reported to security team
- 2026-06-05: patched: Fixed in 2.4.x by r1935004
- 2026-06-08: advisory: Update 2.4.68 released