Listen to this Post
How the CVE Works
CVE-2021-41773 is a path traversal vulnerability in Apache HTTP Server 2.4.49. The flaw arises due to improper normalization of requested paths in the `ap_normalize_path()` function. Attackers can exploit this by sending crafted HTTP requests containing directory traversal sequences (../). If `mod_cgi` is enabled, this could lead to remote code execution (RCE) by allowing unauthorized access to files outside the web root or executing arbitrary scripts. The vulnerability is exploitable when the server is misconfigured to grant excessive permissions.
DailyCVE Form
Platform: Apache HTTP Server
Version: 2.4.49
Vulnerability: Path Traversal → RCE
Severity: Critical
Date: 2021-10-05
Prediction: Patch expected by 2021-10-07
What Undercode Say:
Check Apache version httpd -v Test for traversal (PoC) curl -v "http://target/cgi-bin/.%2e/%2e%2e/%2e%2e/etc/passwd" Mitigation command (update) sudo apt-get upgrade apache2
Exploit:
- Craft HTTP request with `%2e%2e/` (URL-encoded
../) sequences. - Bypass path checks to access `/etc/passwd` or execute scripts via
mod_cgi.
Protection from this CVE:
- Upgrade to Apache 2.4.50+.
- Disable `mod_cgi` if unused.
- Restrict directory permissions.
Impact:
- Unauthorized file disclosure.
- Remote code execution.
- Server compromise.
Sources:
Reported By: www.cve.org
Extra Source Hub:
Undercode
