# CVE-2026-39836: Google Go Denial of Service in net Package on Windows

Source: https://junglewise.ai/threats/cve-2026-39836-google-go-denial-of-service-in-net-package-on-windows  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-07. Updated: 2026-05-14  
License: CC BY 4.0 with a link back

CVE-2026-39836 · Severity: high · CVSS 7.5 · Published 2026-05-07

A vulnerability in the Go programming language's networking library can cause applications running on Windows to crash. If an application uses certain networking functions to process user-supplied input, an attacker could send a specially crafted string containing a null character to trigger a system 'panic' or crash. This results in a denial-of-service, potentially disrupting business operations and service availability.

Technologies: [stdlib (Go)](https://junglewise.ai/threats/technologies/go-stdlib). Vendors: [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-39836 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-39836 being exploited in the wild.

**How severe is CVE-2026-39836?** High severity, with a CVSS score of 7.5, published 7 May 2026.

**Which products and versions are affected?** stdlib (Go) SEMVER:introduced=0,fixed=1.25.10,introduced=1.26.0-0,fixed=1.26.3.

**Is there a fix for CVE-2026-39836?** Yes. stdlib (Go): upgrade to 1.26.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-39836 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-39836?** Check whether you run stdlib (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- stdlib (Go): upgrade to 1.26.3 or later

  ```sh
  go get stdlib@v1.26.3
  ```


## Technical details

A denial-of-service vulnerability exists in the Go standard library 'net' package on Windows platforms. The issue is caused by a NULL pointer dereference (CWE-476) or improper handling of NUL (0) bytes within the Dial and LookupPort functions (and related symbols like DialContext and Resolver.LookupPort). When these functions receive input containing a NUL byte, the runtime triggers a panic instead of returning an error. An unauthenticated remote attacker can exploit this by providing malformed input to network-facing Go applications, causing the process to terminate. The vulnerability is fixed in Go versions 1.25.10 and 1.26.3.

## Affected products

- Google Go < 1.25.10, >= 1.26.0 < 1.26.3

## Identifiers

- CVE-2026-39836
- GO-2026-4971

## Timeline

- 2026-04-29: disclosed: Issue opened on Go GitHub repository
- 2026-05-07: advisory: CVE published and Go security announcement released
- 2026-05-07: patched: Fixes released in Go 1.25.10 and 1.26.3

## References

- [https://go.dev/cl/775320](https://go.dev/cl/775320)
- [https://go.dev/issue/79006](https://go.dev/issue/79006)
- [https://groups.google.com/g/golang-announce/c/qcCIEXso47M](https://groups.google.com/g/golang-announce/c/qcCIEXso47M)
- [https://pkg.go.dev/vuln/GO-2026-4971](https://pkg.go.dev/vuln/GO-2026-4971)

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