CVE-2026-55603
CVE-2026-55603 · http-proxy-middleware: multipart/form-data field injection via unescaped CRLF in `fixRequestBody`
This page contains facts from public vulnerability sources. Check the original advisory before updating.
http-proxy-middleware is node.js http-proxy middleware. From 3.0.4 until 3.0.7 and 4.1.1, fixRequestBody() is the library's documented helper for re-emitting a request body that was already consumed by a body parser. When the outgoing Content-Type is multipart/form-data, it rebuilds the body with handlerFormDataBodyData(), which interpolates each req.body key and value directly into the multipart wire format without neutralizing CR/LF. A \r\n inside a value (or key) lets an attacker close the current part and inject an entirely new form part. Because the proxy's own body parser saw a single opaque value, any gateway-side policy or validation performed on req.body is evaluated against a different set of fields than the upstream backend ultimately parses a request/parameter desynchronization across the trust boundary. This vulnerability is fixed in 3.0.7 and 4.1.1.
CVSS 7.5 · High · EPSS 0.3% · Fix available
- Published
- Updated
Stack: node
Affected products and versions
http-proxy-middleware
- Versions
- >= 3.0.4, < 3.0.7: Affected
- >= 4.0.0, < 4.1.1: Affected
No fix published
http-proxy-middleware npm
- Affected ranges
- SEMVER: ≥ 3.0.4, < 3.0.7
Update to 3.0.7
http-proxy-middleware npm
- Affected ranges
- SEMVER: ≥ 4.0.0, < 4.1.1
Update to 4.1.1