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CVE-2026-43634

7.5 · HIGH

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 addre…

Published May 19, 2026CWE-348EPSS 0.36%

Overview

CVE-2026-43634 is a high-severity vulnerability. It was published on May 19, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/hestiacp/hestiacp/commit/f381e294500f671cf12716c638afd0bfde901f88GitHubgithub.com/hestiacp/hestiacp/issues/5229GitHubgithub.com/hestiacp/hestiacp/pull/5273Refmercuryiss.com.au/hestiacp-unauthenticated-rce-ip-spoofing-cve-2026-43633-cve-2026-43634Refwww.vulncheck.com/advisories/hestiacp-ip-spoofing-via-cf-connecting-ip-header

How CyberStrike helps

Frequently asked questions

What is CVE-2026-43634?

CVE-2026-43634 is a high-severity vulnerability. It was published on May 19, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-43634?

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-43634?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-43634?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-43634 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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