vulnerability / NVI-00013202 / Revision 1
http4k: `reverseProxy()` defaulted to substring (`Contains`) matching on `Host`; tightened to `Exact`
GitHub lists this reviewed advisory for org.http4k:http4k-core, org.http4k:http4k-core, org.http4k:http4k-core. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
org.http4k:http4k-core
source listed>= 5.0.0.0, < 5.42.0.0
### 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 us
org.http4k:http4k-core
source listed< 4.51.0.0
### 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 us
org.http4k:http4k-core
source listed>= 6.0.0.0, < 6.49.0.0
### 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 us
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-jrpc-7vxp-69p6 ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.