CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773)

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. 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 pathes, this could allow for remote code execution. This issue only affects Apache 2.4.49 and Apache 2.4.50 and not earlier versions.

<https://blog.talosintelligence.com/2021/10/apache-vuln-threat-advisory.html&gt;

Recent assessments:

noraj at March 31, 2022 6:44pm UTC reported:

Qualys says:

> CVE-2021-42013 was introduced as the fix for CVE-2021-41773 in Apache HTTP Server 2.4.50 was insufficient as it did not cover double URL encoding, therefore the vulnerable configurations remained the same, but payload used in 2.4.49 was double URL encoded in 2.4.50 to administer the same path traversal and remote code execution attack.
>
> The attack in 2.4.49 initially encoded the second dot (.) to %2e and the same was double URL encoded into %%32%65 for version 2.4.50

Assessed Attacker Value: 5
Assessed Attacker Value: 5Assessed Attacker Value: 5