Listen to this Post
The vulnerability (CVE-2026-XXXX) stems from Undertow’s failure to adequately parse and validate the contents of the HTTP `Host` header. Normally, this header should contain a single, well-formed domain name or IP address. Due to improper parsing logic, an attacker can inject malformed, multiple, or delimited values (e.g., `Host: example.com\r\nHeader-Injection:` or Host: bad.com, good.com). The server processes these requests without rejecting them or normalizing the host value. This allows the malicious payload to propagate through the system, enabling cache poisoning where a reverse proxy might store a response keyed by the poisoned host. It also facilitates attacks like password reset poisoning or internal service request forgery if the host value is used for internal redirects or link generation without validation.
Platform: Undertow (WildFly/JBoss)
Version: Multiple versions
Vulnerability: Host Header Injection
Severity: Critical
date: Jan 7, 2026
Prediction: Patch by 2026-01-28
What Undercode Say:
curl -H "Host: victim.com,attacker.com" http://target/
// Example of unsafe header retrieval
String host = exchange.getRequestHeaders().getFirst("Host");
nmap --script http-host-header-abuse -p 80,443 target
How Exploit:
Cache Poisoning
Password Reset Poisoning
Internal Service SSRF
Protection from this CVE
Apply vendor patch
Implement header sanitization
Use reverse proxy validation
Impact:
Cache Poisoning
Session Hijacking
Internal Network Scan
🎯Let’s Practice Exploiting & Learn Patching For Free:
Sources:
Reported By: github.com
Extra Source Hub:
Undercode
