Vulnerability in Hestiacp
CVE-2026-43634
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.004 (28.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 28th percentile — 28.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.001
Affected products
- Hestiacp — versions 1.2.0, f381e294500f671cf12716c638afd0bfde901f88
Weakness classification (CWE)
References
- mercuryiss.com.au/hestiacp-unauthenticated-rce-ip-spoofing-cve-2026-43633-cve-2… (technical-description, exploit)
- github.com/hestiacp/hestiacp/issues/5229 (issue-tracking)
- github.com/hestiacp/hestiacp/pull/5273 (issue-tracking)
- github.com/hestiacp/hestiacp/commit/f381e294500f671cf12716c638afd0bfde901f88 (patch)
- www.vulncheck.com/advisories/hestiacp-ip-spoofing-via-cf-connecting-ip-header (third-party-advisory)
Frequently asked questions
- What is CVE-2026-43634?
- CVE-2026-43634 is a high-severity vulnerability in Hestiacp, classified under CWE-348. CVSS score: 7.5/10. Published 2026-05-19.
- How severe is CVE-2026-43634?
- High severity. CVSS v3 base score is 7.5 out of 10.