Before the patch, an attacker could send an HTTP request over IPv6 containing:
GET /payment?amount=100&user=alice HTTP/1.1
Host: vulnerable.com
X-Forwarded-For: [2001:db8::1]
Duplicate parameters hidden in IPv6 hop-by-hop options.
The unpached system would:
After applying the HPP v6 patch:
The v6 in "HPP v6 patched" is ambiguous but critical. It most commonly refers to one of two scenarios: hpp v6 patched
If your organization has enabled IPv6 on any public-facing web server or API gateway, you are potentially vulnerable unless you run an HPP v6 patched stack. Before the patch, an attacker could send an
| Technique | Bypasses |
|----------------------------|--------------------------------------------------------------------------|
| Basic duplicate | Only if no duplicate check |
| Case variation | Case-insensitive dedup, case-sensitive backend |
| Encoding | WAF looking for literal ¶m= |
| POST + GET mix | Different sources not normalized together |
| Array syntax | PHP-style parsing without safety |
| HTTP/2 pseudo-headers | Custom proxy or CDN behavior | The unpached system would:
sudo apt-get update
sudo apt-get install libmodsecurity3=3.0.8
SecRule &ARGS "@gt 1" "id:100001,phase:2,deny,msg:'HPP attempt over IPv6',logdata:%MATCHED_VAR_NAME"