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CVE-2026-39825

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

MEDIUM
5.3
CVSS Score
Published: May 7, 2026 at 07:41 PM UTC
Updated: October 26, 2026 at 08:10 PM UTC
2 products affected across 2 vendorsGoGo

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Severity
MEDIUM5.3
Exploit prediction
EPSS 0.4%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Go· Golang
95%
v < 1.25.101.26.0 ≤ v < 1.26.3
Go· Go Standard Librarygo
90%
v < 1.25.101.26.0-0 ≤ v < 1.26.31.26.0-0
Affected range stops below 1.25.10, so it looks safe — our inference, not a vendor statement
Affected range stops below 1.26.3, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (4)

Patch
Source: cverecord
https://go.dev/cl/770541
Issue Tracking
Source: cverecord
https://go.dev/issue/78948
Release Notes
Source: cverecord
https://groups.google.com/g/golang-announce/c/qcCIEXso47M
Vendor Advisory
Source: cverecord
https://pkg.go.dev/vuln/GO-2026-4976

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.3MEDIUMCISA-ADP
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
LOW
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
NVD-CWE-noinfo

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