{"items":[{"id":"NVI-00017751","kind":"vulnerability","title":"http-proxy-middleware `router` host+path substring matching allows Host-header-driven backend routing bypass","revision":1,"unknowns":["Customer inventory, deployment, reachability and exploitation have not been inspected."],"lifecycle":"active","identifiers":["GHSA-64mm-vxmg-q3vj","CVE-2026-55602"],"plain_summary":"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.","review_status":"source_listed","control_topics":[],"public_actions":[{"summary":"Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.","source_ids":["sr-5b56ad76d2522c5f1cca8ea3bc051d67"],"action_type":"investigate","limitations":"Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system.","current_supported_target":null}],"schema_version":"1.1.0","source_metrics":[],"why_it_matters":"Published affected context helps an owner decide what evidence to gather. This report has not examined your application.","related_sources":[{"id":"sr-5b56ad76d2522c5f1cca8ea3bc051d67","url":"https://github.com/advisories/GHSA-64mm-vxmg-q3vj","basis":"vendor_advisory","notes":"GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.","title":"GHSA-64mm-vxmg-q3vj","publisher":"GitHub Advisory Database","observed_at":"2026-11-05T19:06:16.668Z"}],"affected_context":[{"certainty":"source_listed","source_ids":["sr-5b56ad76d2522c5f1cca8ea3bc051d67"],"technology":"http-proxy-middleware","known_exclusions":[],"conditions_summary":"# Summary\n\n`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.\n\n# Details\n\nTested code state:\n\n- validated on tag `v4.0.0-beta.5`\n- corresponding commit: `339f09ede860197807d4fd99ed9020fa5d0bd358`\n\nRelevant code locations:\n\n- `src/router.ts`\n- `src/http-proxy-middleware.ts`\n\nAffected public API:\n\n- `createProxyMiddleware({ router: { 'host/path': 'http://target' } })`\n\nCode explanation:\n\nWhen 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:\n\n```ts\nhostAndPath.indexOf(key) > -1\n```\n\nThat is a substring test, not an exact host match plus intended path match. In the validated PoC, the configured router key is:\n\n```txt\nlocalhost:3000/api\n```\n\nbut the attacker-controlled host is:\n\n```txt\nevillocalhost:3000\n```\n\nand the request path is:\n\n","public_affected_ranges":[">= 4.0.0, < 4.1.0"]},{"certainty":"source_listed","source_ids":["sr-5b56ad76d2522c5f1cca8ea3bc051d67"],"technology":"http-proxy-middleware","known_exclusions":[],"conditions_summary":"# Summary\n\n`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.\n\n# Details\n\nTested code state:\n\n- validated on tag `v4.0.0-beta.5`\n- corresponding commit: `339f09ede860197807d4fd99ed9020fa5d0bd358`\n\nRelevant code locations:\n\n- `src/router.ts`\n- `src/http-proxy-middleware.ts`\n\nAffected public API:\n\n- `createProxyMiddleware({ router: { 'host/path': 'http://target' } })`\n\nCode explanation:\n\nWhen 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:\n\n```ts\nhostAndPath.indexOf(key) > -1\n```\n\nThat is a substring test, not an exact host match plus intended path match. In the validated PoC, the configured router key is:\n\n```txt\nlocalhost:3000/api\n```\n\nbut the attacker-controlled host is:\n\n```txt\nevillocalhost:3000\n```\n\nand the request path is:\n\n","public_affected_ranges":[">= 3.0.0, < 3.0.6"]},{"certainty":"source_listed","source_ids":["sr-5b56ad76d2522c5f1cca8ea3bc051d67"],"technology":"http-proxy-middleware","known_exclusions":[],"conditions_summary":"# Summary\n\n`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.\n\n# Details\n\nTested code state:\n\n- validated on tag `v4.0.0-beta.5`\n- corresponding commit: `339f09ede860197807d4fd99ed9020fa5d0bd358`\n\nRelevant code locations:\n\n- `src/router.ts`\n- `src/http-proxy-middleware.ts`\n\nAffected public API:\n\n- `createProxyMiddleware({ router: { 'host/path': 'http://target' } })`\n\nCode explanation:\n\nWhen 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:\n\n```ts\nhostAndPath.indexOf(key) > -1\n```\n\nThat is a substring test, not an exact host match plus intended path match. In the validated PoC, the configured router key is:\n\n```txt\nlocalhost:3000/api\n```\n\nbut the attacker-controlled host is:\n\n```txt\nevillocalhost:3000\n```\n\nand the request path is:\n\n","public_affected_ranges":[">= 0.16.0, < 2.0.10"]}],"null_published_at":"2026-11-05T19:10:21.463Z","source_updated_at":"2026-06-23T10:15:39.000Z","source_disclosed_at":"2026-06-18T13:06:11.000Z","is_synthetic_fixture":false,"null_last_reviewed_at":null,"public_change_summary":"First indexed by Null; source disclosure date is shown separately.","null_first_observed_at":"2026-11-05T19:06:16.668Z"}],"next_cursor":null,"snapshot_revision":"42594"}