The Apache Software Foundation rolled out additional security update for its Apache HTTP server to address an actively exploited path traversal and remote code execution vulnerability (CVE-2021-41773) that the organization says was only partially fixed earlier this week.

“It was found that the fix for CVE-2021-41773 in Apache HTTP Server 2.4.50 was insufficient. An attacker could use a path traversal attack to map URLs to files outside the directories configured by Alias-like directives,” Apache said.

“If files outside of these directories are not protected by the usual default configuration "require all denied", these requests can succeed. If CGI scripts are also enabled for these aliased patches, this could allow for remote code execution.”

This issue only affects Apache 2.4.49 and Apache 2.4.50 and not earlier versions.

The new issue, tracked as CVE-2021-42013, builds upon CVE-2021-41773, the path traversal issue that could allow an attacker to map URLs to files outside the expected document root.

The United States Computer Emergency Readiness Team (US-CERT) warned on Thursday that threat actors are actively scanning the internet for Apache HTTP Servers vulnerable to CVE-2021-41773 and CVE-2021-42013.

“Active scanning of Apache HTTP Server CVE-2021-41773 & CVE-2021-42013 is ongoing and expected to accelerate, likely leading to exploitation. Please patch immediately if you haven’t already—this cannot wait until after the weekend,” US-CERT tweeted.