ReverseProxy can forward queries containing parameters not visible to Rewrite functions. When used with a Rewrite function, or a Director function which parses query parameters, ReverseProxy sanitizes the forwarded request to remove query parameters which are not parsed by url.ParseQuery. ReverseProxy does not take ParseQuery's limit on the total number of query parameters (controlled by GODEBUG=urlmaxqueryparams=N) into account. This can permit ReverseProxy to forward a request containing a query parameter that is not visible to the Rewrite function. For example, the query "a1=x&a2=x&...&a10000=x&hidden=y" can forward the parameter "hidden=y" while hiding it from the proxy's Rewrite function.
Fix
Patch, vendor advisory and mitigation references on NVD 2
- https://go.dev/cl/770541 Patch
- https://pkg.go.dev/vuln/GO-2026-4976 Vendor Advisory
Every line above is quoted from NVD, CISA, Microsoft, the vendor's own advisory or DISA; nothing is generated.
Change history 1
- First seenCVSS 5.3 · golangNVD modified 2026-10-26 20:10
Affected (CPE criteria) 1
cpe:2.3:a:golang:go:*:*:*:*:*:*:*:*
References 4
- https://go.dev/cl/770541 Patch
- https://go.dev/issue/78948 Issue Tracking
- https://groups.google.com/g/golang-announce/c/qcCIEXso47M Release Notes
- https://pkg.go.dev/vuln/GO-2026-4976 Vendor Advisory