Vulnerability Description
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 Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Chimurai | Http-Proxy-Middleware | >= 3.0.4, < 3.0.7 |
Related Weaknesses (CWE)
References
- https://github.com/chimurai/http-proxy-middleware/security/advisories/GHSA-gcq2-ExploitMitigationVendor Advisory
- https://github.com/chimurai/http-proxy-middleware/security/advisories/GHSA-gcq2-ExploitMitigationVendor Advisory
FAQ
What is CVE-2026-55603?
CVE-2026-55603 is a vulnerability with a CVSS score of 7.5 (HIGH). 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 b...
How severe is CVE-2026-55603?
CVE-2026-55603 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-55603?
Check the references section above for vendor advisories and patch information. Affected products include: Chimurai Http-Proxy-Middleware.