http4k before 6.49.0.0 Host Header Routing Bypass via reverseProxy
Published Sep 27, 2026
6.3
MEDIUMCVSS 4.0
EPSS 0.34%
Description
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 products
No data.
No data.
No data.
No Red Hat product state for this CVE.
No package ranges for this CVE.
Remediation
No remediation recorded yet.
Metrics
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
No CVSS v3.0 score for this CVE.
No CVSS v2.0 score for this CVE.
This CVE is not in the KEV list.
CISA SSVC (Vulnrichment)
Stakeholder-Specific Vulnerability Categorization from CISA ADP.
Exploitation
NoneAutomatable
NoTechnical Impact
PartialDecision
n/aAssessed Sep 30, 2026 · SSVC 2.0.3
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 2, 2026.
Score over time
Oct 2026- EPSS v5
Percentile over time
- EPSS v5
Table of values (2 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 2, 2026 | 0.34% (0.00344) | 25.58th | v5 (v2026.06.15) |
| Oct 1, 2026 | 0.34% (0.00344) | 25.49th | v5 (v2026.06.15) |
References (4)
- https://github.com/http4k/http4k/commit/0121b05537 patch
- https://github.com/http4k/http4k/commit/54c6385615 patch
- https://github.com/http4k/http4k/security/advisories/GHSA-jrpc-7vxp-69p6 vendor-advisory
- https://www.vulncheck.com/advisories/http4k-before-6.49.0.0-host-header-routing-bypass-via-reverseproxy third-party-advisory
| Link | Providers | Tags |
|---|---|---|
| https://github.com/http4k/http4k/commit/0121b05537 | patch | |
| https://github.com/http4k/http4k/commit/54c6385615 | patch | |
| https://github.com/http4k/http4k/security/advisories/GHSA-jrpc-7vxp-69p6 | vendor-advisory | |
| https://www.vulncheck.com/advisories/http4k-before-6.49.0.0-host-header-routing-bypass-via-reverseproxy | third-party-advisory |
Change history (0)
No recorded changes yet.