CVE-2026-39825
Description
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.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
Vendor advisory: suse — https://www.suse.com/security/cve/CVE-2026-39825.html
Vendor advisory: debian — https://security-tracker.debian.org/tracker/CVE-2026-39825
Vendor advisory: security@golang.org — https://pkg.go.dev/vuln/GO-2026-4976
Vendor advisory: security@golang.org — https://groups.google.com/g/golang-announce/c/qcCIEXso47M
Vendor advisory: security@golang.org — https://go.dev/cl/770541
OS impact
| OS | Version | Status | Fixed in |
|---|---|---|---|
| debian | trixie | affected | |
| debian | bullseye | affected | |
| debian | bookworm | affected | |
| debian | forky | fixed | 1.25.10-1 |
| debian | sid | fixed | 1.25.10-1 |
| sles | affected | |
Package impact
| Ecosystem | Package | Vulnerable | Fixed |
|---|---|---|---|
| Go | stdlib | >=1.26.0-0,<1.26.3 | 1.25.10 |
References
Verify integrity in audit chain (admin only). AS-IS.