http-proxy-middleware: multipart/form-data field injection via unescaped CRLF in `fixRequestBody`

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Summary

CVECVE-2026-55603
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-22 21:16:26 UTC
Updated2026-06-22 21:16:26 UTC
Descriptionhttp-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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N

Problem Types: CWE-93 | CWE-93 CWE-93: Improper Neutralization of CRLF Sequences ('CRLF Injection')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
Low
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Chimurai Http-proxy-middleware affected >= 3.0.4, < 3.0.7 Not specified
CNA Chimurai Http-proxy-middleware affected >= 4.0.0, < 4.1.1 Not specified

References

ReferenceSourceLinkTags
github.com/chimurai/http-proxy-middleware/security/advisories/GHSA-gcq2-... [email protected] github.com
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