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🛡️ CVE-2026-39825 — go

🟡 CVSS 5.3 — Medium ✅ No Known Exploit NVD
5.3
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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

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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality low, integrity none, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: Low — limited, and the attacker does not choose what is affected.
  • Integrity impact: None.
  • Availability impact: None.

Affected software

CVE-2026-39825 is recorded against 3 packages.

  • go (from 1.26.0 up to 1.26.3)
  • golang
  • stdlib

Timeline and source

Published on 7 May 2026 and last revised on 17 June 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

go.dev
go.dev
groups.google.com
pkg.go.dev

Other advisories for this package

go has other advisories on record. If you are patching this one, these are worth checking on the same host:

CVE-2026-39825 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity MEDIUM
CVSS Score 5.3
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
CWE N/A
Public Exploit ✅ No
Source NVD
Published 2026-05-07
Updated 2026-08-20
Modified 2026-06-17

Affected Packages

Software From version Fixed in
go 1.26.0 1.26.3
golang — —
stdlib — —

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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