CVE-2026-39825 ReverseProxy forwards queries with more than urlmaxqueryparams parameters in net/http/httputil
ReverseProxy in Go's net/http/httputil may forward hidden query parameters, bypassing Rewrite function sanitization checks.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-39825?
CVE-2026-39825 is a medium-severity vulnerability in Golang Go, published on 7 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-39825?
2 open source packages ship an affected version, including golang and stdlib. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
golang Bitnami | All versions | 1.25.10, 1.26.3 |
stdlib Go | All versions | 1.25.10, 1.26.3 |
Products include Golang Go.
How do I fix CVE-2026-39825?
Upgrade golang to a fixed version for your release line: 1.25.10 or 1.26.3.
Is CVE-2026-39825 being exploited?
There is no known exploitation of CVE-2026-39825 in the wild and no public exploit code.
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Sources
Also known as AZL-98652, BELL-CVE-2026-39825, BIT-golang-2026-39825, CLEANSTART-2026-AP95422, CLEANSTART-2026-EL93151, CLEANSTART-2026-FO79285 and 795 more.