# CVE-2026-43634

## Summary

- **CVE ID:** CVE-2026-43634
- **Severity:** HIGH
- **CVSS Score:** 8.7 (CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N)
- **CWE:** CWE-348
- **Published:** May 19, 2026
- **Last Modified:** Jul 14, 2026

## Description

HestiaCP versions 1.2.0 through 1.9.4 contain an IP spoofing vulnerability that allows unauthenticated remote attackers to bypass authentication security controls by supplying an arbitrary IP address in the CF-Connecting-IP HTTP header without verifying the request originated from Cloudflare's network. Attackers can exploit this to circumvent fail2ban brute-force protection, bypass per-user IP allowlists, and poison authentication audit logs by spoofing trusted IP addresses on each request.

## Affected Products

- hestiacp — hestiacp (1.2.0)
- hestiacp — hestiacp (f381e294500f671cf12716c638afd0bfde901f88)

## References

- [CNA](https://mercuryiss.com.au/hestiacp-unauthenticated-rce-ip-spoofing-cve-2026-43633-cve-2026-43634)
- [CNA](https://github.com/hestiacp/hestiacp/issues/5229)
- [CNA](https://github.com/hestiacp/hestiacp/pull/5273)
- [CNA](https://github.com/hestiacp/hestiacp/commit/f381e294500f671cf12716c638afd0bfde901f88)
- [CNA](https://www.vulncheck.com/advisories/hestiacp-ip-spoofing-via-cf-connecting-ip-header)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.24%
- **EPSS Percentile:** 15.2

---
_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._