Full Report
Learn how to protect cloud environments from the new critical Apache HTTP Server vulnerability.
Analysis Summary
# Vulnerability: Apache HTTP Server Path Traversal and File Disclosure
## CVE Details
- CVE ID: CVE-2021-41773, CVE-2021-42013 (CVE-2021-42013 assigned to the insufficient fix in 2.4.50)
- CVSS Score: N/A (Severity implied as high due to RCE exploitation)
- CWE: Path Traversal (CWE-22 likely)
## Affected Systems
- Products: Apache HTTP Server
- Versions: 2.4.49, 2.4.50 (The initial fix in 2.4.50 was insufficient and is also vulnerable)
- Configurations: Applicable to installations used as web servers.
## Vulnerability Description
The vulnerability stems from a change in path normalization within Apache HTTP Server version 2.4.49. It allows an attacker to perform a path traversal attack, enabling them to map URLs to files outside the intended document root. Successful exploitation can lead to disclosure of arbitrary files on the server, and in some cases, exploitation has led to remote code execution (RCE) via access to source files interpreted as CGI scripts.
## Exploitation
- Status: Exploited in the wild (Multiple exploits published, including RCE)
- Complexity: Low to Medium (Implied due to rapid publication of PoCs and active scanning)
- Attack Vector: Adjacent (Typically Network via HTTP requests)
## Impact
- Confidentiality: High (Allows access to sensitive files, configurations, and potentially cloud credentials/keys)
- Integrity: High (Potential for remote code execution bypasses integrity controls)
- Availability: Medium (Can lead to system disruption, but primary immediate risk is data exposure/takeover)
## Remediation
### Patches
- Update to **Apache HTTP Server version 2.4.51** or later.
- Version 2.4.49 is vulnerable.
- Version 2.4.50 (the first fix) is also vulnerable/bypassable.
### Workarounds
- Disable the vulnerable resource.
- Block all internet access to the affected server instance.
- **For Cloud Environments:** Ensure internet-facing workloads have the most limited permissions possible. Avoid storing overly permissive secrets (like admin cloud keys) on disk; use secure alternatives like metadata services where possible.
## Detection
- **Indicators of Compromise (IoCs):** Scanning activity targeting Apache HTTP Server, requests containing path traversal sequences (e.g., `../`), and unexpected file access logs originating from web requests.
- **Detection Methods and Tools:** Inventory scanning to identify all installations of Apache HTTP Server versions 2.4.49 and 2.4.50. Look for sensitive secrets (cloud keys, database credentials) exposed on disk near web roots, as attackers exploit this vulnerability to find such secrets.
## References
- Vendor advisory: http://httpd.apache.org/security/vulnerabilities_24.html#CVE-2021-41773
- General security guidance available regarding CVE-2021-41773 and CVE-2021-42013.