CVE Catalog

CVE-2026-39825

MediumCVSS 5.3
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.39%

33th percentile - higher than 33% of all known CVEs

Summary

Go's ReverseProxy can forward queries containing parameters not visible to Rewrite functions. It does not account for ParseQuery's limit on total query parameters (GODEBUG=urlmaxqueryparams=N), allowing a request with a hidden parameter such as hidden=y to be forwarded while hidden from the Rewrite function.

Risk Assessment

An attacker could smuggle query parameters that bypass security logic in Rewrite functions, potentially leading to access control bypass or data injection. This may compromise applications using ReverseProxy.

Recommendation

Upgrade Go to a version containing the fix or adjust GODEBUG=urlmaxqueryparams configuration to account for the limit in ReverseProxy. Review Rewrite functions for susceptibility to hidden parameters.

Related vulnerabilities

Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS