GHSA-jrpc-7vxp-69p6
http4k: `reverseProxy()` defaulted to substring (`Contains`) matching on `Host`; tightened to `Exact`
Blast Radius
org.http4k:http4k-core☕org.http4k:http4k-core☕org.http4k:http4k-coreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Impact
reverseProxy() and reverseProxyRouting() matched configured vhosts by substring on the Host header (Contains matcher) by default. The intended use of these functions in http4k is outbound dispatch (e.g. matching AWS service subdomains, per the Contains docstring) and test-time composition of fake backend networks. In either of those contexts the matched Host is set by the calling application, not by an external attacker, so the loose match has no exploit surface.
If, however, reverseProxy() was deployed as a public-facing inbound HTTP handler — which the function technically supports but is not the documented intent — an external attacker could send Host: admin.evil.com and reach a vhost configured as admin, bypassing routing-based authorization.
The Contains matcher's docstring explicitly documented this loose behaviour, but because Contains was the default, callers who never read the matcher docs would still get the loose behaviour.
Who is affected: only deployments using reverseProxy() / reverseProxyRouting() as a public-facing inbound HTTP handler with two or more configured virtual hosts. The intended outbound / test-time usage is unaffected. If you did deploy reverseProxy() inbound and rely on multi-vhost routing for authorization, treat upgrade as urgent.
Patches
| Line | Fixed in | Edition |
|---|---|---|
| v6.x (Community) | 6.49.0.0 | Community |
| v5.x (LTS) | 5.42.0.0 | Enterprise — contact [email protected] (if reverseProxy() is present in your v5.x line) |
| v4.x (LTS) | 4.51.0.0 | Enterprise — contact [email protected] (if reverseProxy() is present in your v4.x line) |
The fix changes the default matcher to Exact. Existing callers that genuinely need substring matching (e.g. AWS subdomain dispatch) must explicitly pass matcher = Contains.
Workarounds
For deployments that cannot upgrade immediately: wrap your reverseProxy() with a host-allow-list filter that requires an exact match against expected vhost names before delegating.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.http4k:http4k-core | ≥ 6.0.0.0&&< 6.49.0.0 | 6.49.0.0 |
| ☕Maven | org.http4k:http4k-core | ≥ 5.0.0.0&&< 5.42.0.0 | 5.42.0.0 |
| ☕Maven | org.http4k:http4k-core | all versions | 4.51.0.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.http4k:http4k-core. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.http4k:http4k-core to 6.49.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-jrpc-7vxp-69p6 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-jrpc-7vxp-69p6 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-jrpc-7vxp-69p6. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-jrpc-7vxp-69p6 in your dependencies?
O3 detects GHSA-jrpc-7vxp-69p6 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.