vulnerability / NVI-00017751 / Revision 1
http-proxy-middleware `router` host+path substring matching allows Host-header-driven backend routing bypass
GitHub lists this reviewed advisory for http-proxy-middleware, http-proxy-middleware, http-proxy-middleware. 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.
http-proxy-middleware
source listed>= 4.0.0, < 4.1.0
# Summary `http-proxy-middleware` documents `router` proxy-table entries as host, path, or host+path selectors, but the host+path implementation uses unanchored substring matching on attacker-controlled request metadata. As a result, a crafted `Host` header that is only a superstring match for a configured host+path key can still route a request to an unintended backend. # Details Tested code state: - validated on tag `v4.0.0-beta.5` - corresponding commit: `339f09ede860197807d4fd99ed9020fa5d0bd358` Relevant code locations: - `src/router.ts` - `src/http-proxy-middleware.ts` Affected public API: - `createProxyMiddleware({ router: { 'host/path': 'http://target' } })` Code explanation: When a proxy-table router key contains `/`, `getTargetFromProxyTable()` concatenates attacker-controlled `req.headers.host` and `req.url` into a single `hostAndPath` string, then accepts the route if: ```ts hostAndPath.indexOf(key) > -1 ``` That is a substring test, not an exact host match plus intended path match. In the validated PoC, the configured router key is: ```txt localhost:3000/api ``` but the attacker-controlled host is: ```txt evillocalhost:3000 ``` and the request path is:
http-proxy-middleware
source listed>= 3.0.0, < 3.0.6
# Summary `http-proxy-middleware` documents `router` proxy-table entries as host, path, or host+path selectors, but the host+path implementation uses unanchored substring matching on attacker-controlled request metadata. As a result, a crafted `Host` header that is only a superstring match for a configured host+path key can still route a request to an unintended backend. # Details Tested code state: - validated on tag `v4.0.0-beta.5` - corresponding commit: `339f09ede860197807d4fd99ed9020fa5d0bd358` Relevant code locations: - `src/router.ts` - `src/http-proxy-middleware.ts` Affected public API: - `createProxyMiddleware({ router: { 'host/path': 'http://target' } })` Code explanation: When a proxy-table router key contains `/`, `getTargetFromProxyTable()` concatenates attacker-controlled `req.headers.host` and `req.url` into a single `hostAndPath` string, then accepts the route if: ```ts hostAndPath.indexOf(key) > -1 ``` That is a substring test, not an exact host match plus intended path match. In the validated PoC, the configured router key is: ```txt localhost:3000/api ``` but the attacker-controlled host is: ```txt evillocalhost:3000 ``` and the request path is:
http-proxy-middleware
source listed>= 0.16.0, < 2.0.10
# Summary `http-proxy-middleware` documents `router` proxy-table entries as host, path, or host+path selectors, but the host+path implementation uses unanchored substring matching on attacker-controlled request metadata. As a result, a crafted `Host` header that is only a superstring match for a configured host+path key can still route a request to an unintended backend. # Details Tested code state: - validated on tag `v4.0.0-beta.5` - corresponding commit: `339f09ede860197807d4fd99ed9020fa5d0bd358` Relevant code locations: - `src/router.ts` - `src/http-proxy-middleware.ts` Affected public API: - `createProxyMiddleware({ router: { 'host/path': 'http://target' } })` Code explanation: When a proxy-table router key contains `/`, `getTargetFromProxyTable()` concatenates attacker-controlled `req.headers.host` and `req.url` into a single `hostAndPath` string, then accepts the route if: ```ts hostAndPath.indexOf(key) > -1 ``` That is a substring test, not an exact host match plus intended path match. In the validated PoC, the configured router key is: ```txt localhost:3000/api ``` but the attacker-controlled host is: ```txt evillocalhost:3000 ``` and the request path is:
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-64mm-vxmg-q3vj ↗
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.