Zero-day vulnerability in Apache HTTP Server

Path traversal
CVE-2021-41773

Vulnerability details

Advisory: SB2021100514 - Multiple vulnerabilities in Apache HTTP Server

Vulnerable component: Apache HTTP Server

CVE-ID: CVE-2021-41773

CVSSv3 score: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:H/RL:O/RC:C

CWE-ID: CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

Description:

The vulnerability allows a remote attacker to perform directory traversal attacks.

The vulnerability exists due to input validation error when processing directory traversal sequences. A remote attacker can send a specially crafted HTTP request to map URLs to files outside the expected document root. If files outside of the document root are not protected by "require all denied" these requests can succeed. Additionally this flaw could leak the source of interpreted files like CGI scripts.

The vulnerability can be used to execute arbitrary OS commands on the system.

Note, the vulnerability is being actively exploited in the wild.

Public Exploits:

- Apache HTTP Server 2.4.49 - Path Traversal & Remote Code Execution (RCE) [Exploit-DB]

- Apache HTTP Server 2.4.50 - Remote Code Execution (RCE) (3) [Exploit-DB]

External links:

https://httpd.apache.org/security/vulnerabilities_24.html

About zero-day vulnerabilities

Zero-day vulnerability is an undisclosed vulnerability in software that hackers can exploit to compromise computer programs, gain unauthorized access to sensitive data, penetrate networks, etc. We consider vulnerability a zero-day when there is no solution provided from software vendor and the vulnerability is being actively exploited by malicious actors.

Zero-day candidate is a potential zero-day vulnerability in software which might have been used in targeted attacks, however there is no evidence to support this suggestion.