http4k before 6.49.0.0 Host Header Routing Bypass via reverseProxy
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.
CVE-2026-100724
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-100724
http4k
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
http4k
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
http4k
Source reference: /containers/cna/affected/2/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"vendor": "http4k",
"product": "http4k",
"versions": [
{
"status": "affected",
"version": "0",
"lessThan": "6.49.0.0",
"versionType": "custom"
},
{
"status": "unaffected",
"version": "6.49.0.0",
"versionType": "custom"
}
],
"packageURL": "pkg:maven/org.http4k/http4k-core",
"defaultStatus": "unaffected"
},
{
"vendor": "http4k",
"product": "http4k",
"versions": [
{
"status": "affected",
"version": "0",
"lessThan": "5.42.0.0",
"versionType": "custom"
},
{
"status": "unaffected",
"version": "5.42.0.0",
"versionType": "custom"
}
],
"packageURL": "pkg:maven/org.http4k/http4k-core",
"defaultStatus": "unaffected"
},
{
"vendor": "http4k",
"product": "http4k",
"versions": [
{
"status": "affected",
"version": "0",
"lessThan": "4.51.0.0",
"versionType": "custom"
},
{
"status": "unaffected",
"version": "4.51.0.0",
"versionType": "custom"
}
],
"packageURL": "pkg:maven/org.http4k/http4k-core",
"defaultStatus": "unaffected"
}
]- Related CVEs
- CVE-2026-100724
Source reference:
/cveMetadata/cveId
Publisher severity
medium
Source reference: /containers/cna/metrics
- Event
- #4448 · Revision 1
- Added to Heist Feed
- Publisher date