{"id":"CVE-2026-55603","summary":"http-proxy-middleware: multipart/form-data field injection via unescaped CRLF in `fixRequestBody`","details":"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.","aliases":["GHSA-gcq2-9pq2-cxqm"],"modified":"2026-07-08T08:14:00.544219007Z","published":"2026-06-22T20:07:05.034Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55603.json","cna_assigner":"GitHub_M","cwe_ids":["CWE-93"]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55603.json"},{"type":"ADVISORY","url":"https://github.com/chimurai/http-proxy-middleware/security/advisories/GHSA-gcq2-9pq2-cxqm"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55603"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/chimurai/http-proxy-middleware","events":[{"introduced":"01934d33b157b2d49f7099a18ceec165e7502040"},{"fixed":"8cc4eba839e6cd95ebc073b2b48c4124ed72c302"},{"introduced":"8f356bcb5fce079460564f729da55814363361a6"},{"fixed":"b3b98d2846aa6a0cc9a1a08b8b152a634bb4741e"}],"database_specific":{"source":"CPE_RANGE","cpe":"cpe:2.3:a:chimurai:http-proxy-middleware:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"3.0.4"},{"fixed":"3.0.7"},{"introduced":"4.0.0"},{"fixed":"4.1.1"}]}}],"versions":["v4.1.0","v3.0.6","v4.1.0-beta.2","v4.1.0-beta.1","v4.1.0-beta.0","v4.0.0","v3.0.5","v3.0.4"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55603.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N"}]}