http4k before 6.49.0.0 Host Header Routing Bypass via reverseProxy
Impact
http4k before 6.49.0.0, 5.42.0.0, and 4.51.0.0 has a routing bypass vulnerability via reverseProxy. A remote attacker can supply a Host header containing a configured vhost name to bypass routing-based authorization.
Summarized by @cf/meta/llama-3.3-70b-instruct-fp8-fast. Verify details against the original sources.Affected packages
Affected products
Vendor version evidence. Product records are separate from automatic dependency matching.
http4k · VulnCheck
http4k
2 ranges
http4k · VulnCheck
http4k
Package identity
pkg:maven/org.http4k/http4k-coreExplore org.http4k:http4k-core →Identity supplied by VulnCheck. Version matching requires compatible range evidence.
Compare with this publisher’s ranges. This does not inspect your installation.
affected
6.0.0.0 → before 6.49.0.0
custom versions
unaffected
6.49.0.0
custom versions
Other versions: unaffected
http4k · VulnCheck
http4k
2 ranges
http4k · VulnCheck
http4k
Package identity
pkg:maven/org.http4k/http4k-coreExplore org.http4k:http4k-core →Identity supplied by VulnCheck. Version matching requires compatible range evidence.
Compare with this publisher’s ranges. This does not inspect your installation.
affected
5.0.0.0 → before 5.42.0.0
custom versions
unaffected
5.42.0.0
custom versions
Other versions: unaffected
http4k · VulnCheck
http4k
2 ranges
http4k · VulnCheck
http4k
Package identity
pkg:maven/org.http4k/http4k-coreExplore org.http4k:http4k-core →Identity supplied by VulnCheck. Version matching requires compatible range evidence.
Compare with this publisher’s ranges. This does not inspect your installation.
affected
0 → before 4.51.0.0
custom versions
unaffected
4.51.0.0
custom versions
Other versions: unaffected
Original source 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.
Inside the record
Evidence available
Describes the evidence in this view, not whether the product is safe.
Original records
CVE-2026-100724View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.
cve.new JSON →Underlying weaknesses
The source’s classification of what caused the vulnerability.
Contributing organizations · 2
Assigning organization
Additional data publisher
What changed
Follow changesLarge field values are marked as truncated previews. Original source snapshots remain retained.