CVE-2026-100724: http4k before 6.49.0.0 Host Header Routing Bypass via reverseProxy
Fixed in 6.49.0.0 · Affected: http4k before 6.49.0.0 · Exploitation: unlikely (under 1%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 28% of scored CVEs
DescriptionCVE.org
http4k (Maven package org.http4k:http4k-core) before 6.49.0.0, 5.42.0.0 and 4.51.0.0 uses substring (Contains) matching on the Host header by default in reverseProxy() and reverseProxyRouting() when dispatching to configured virtual hosts. If these functions are deployed as a public-facing inbound HTTP handler with two or more configured virtual hosts, a remote attacker can supply a Host header that merely contains a configured vhost name (for example Host: admin.evil.com for a vhost configured as "admin") and be routed to that vhost, bypassing routing-based authorization. The intended outbound-dispatch and test-time uses, where the Host value is set by the calling application, are not affected.
Affected products3
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- http4k · http4kfrom 6.0.0.0 before 6.49.0.0
- http4k · http4kfrom 5.0.0.0 before 5.42.0.0
- http4k · http4kbefore 4.51.0.0
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Unlikely (under 1%). EPSS under 1%, or no score yet.
- CISA KEV
- Not listed
- Public check
- No public nuclei template
- Vendor
- http4k
- Published
- September 2026
CoverageNo articles yet
No CyberSIXT article names CVE-2026-100724 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.