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CVE-2026-39825GO-2026-4976BIT-GOLANG-2026-39825

ReverseProxy forwards queries with more than urlmaxqueryparams parameters in net/http/httputil

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 1.25.10, 1.26.3
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: yes
  • Technical impact: partial

Summary

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: yes · Technical impact: partial

  3. Record last updated

Affected versions

  • net/http/httputil

    fixed in 1.25.10; From 1.26.0-0 · fixed in 1.26.3

  • stdlibGo

    fixed in 1.25.10; From 1.26.0-0 · fixed in 1.26.3

References 4

go.dev

groups.google.com

pkg.go.dev