How the CVE Works:
The vulnerability resides in the `/3/ImportFiles` endpoint of H2O version 3.46.1. The endpoint accepts a GET parameter, path, which can be manipulated to reference itself recursively. When an attacker sends a crafted request with the `path` parameter pointing back to the same endpoint, the server enters an infinite loop of self-referential calls. This exhausts the server’s request queue, consuming all available resources and rendering the server unresponsive to legitimate requests. The lack of proper input validation and recursion checks in the endpoint’s implementation allows this exploit to occur, leading to a Denial of Service (DoS) condition.
DailyCVE Form:
Platform: H2O
Version: 3.46.1
Vulnerability: Denial of Service (DoS)
Severity: High
Date: Mar 20, 2025
What Undercode Say:
Exploitation:
1. Crafting the Malicious Request:
An attacker can exploit this vulnerability by sending a GET request to the `/3/ImportFiles` endpoint with the `path` parameter set to reference itself. For example:
curl -X GET "http://target-server/3/ImportFiles?path=/3/ImportFiles?path=..."
This creates a recursive loop, overwhelming the server.
2. Automating the Attack:
Use a script to repeatedly send the malicious request:
import requests target_url = "http://target-server/3/ImportFiles?path=/3/ImportFiles?path=..." while True: requests.get(target_url)
Protection:
1. Input Validation:
Implement strict input validation to prevent recursive references in the `path` parameter. For example:
def validate_path(path):
if "ImportFiles" in path:
raise ValueError("Invalid path: recursive reference detected")
2. Rate Limiting:
Apply rate limiting to the `/3/ImportFiles` endpoint to mitigate abuse:
location /3/ImportFiles {
limit_req zone=one burst=5 nodelay;
}
3. Patch Application:
Upgrade to the latest version of H2O where this vulnerability is patched. Check the official repository for updates:
git pull origin master
4. Monitoring and Logging:
Enable detailed logging to detect and block suspicious activity:
tail -f /var/log/h2o/access.log | grep "3/ImportFiles"
5. Web Application Firewall (WAF):
Deploy a WAF to filter out malicious requests:
Example WAF rule for ModSecurity SecRule ARGS:path "@contains /3/ImportFiles" "id:1001,deny,status:403"
6. Resource Limits:
Set resource limits to prevent the server from being overwhelmed:
ulimit -n 1024 Limit open file descriptors
By following these steps, you can mitigate the risk of this vulnerability and protect your H2O server from exploitation.
References:
Reported By: https://github.com/advisories/GHSA-p2vc-m5fv-9w9m
Extra Source Hub:
Undercode
