# CVE-2026-94439: Go net/http HTTP/1 server CONNECT response desynchronization

Source: https://junglewise.ai/threats/cve-2026-94439-go-2026-6613-http-1-server-connection-desynchronization-after-2xx  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-08. Updated: 2026-10-10  
License: CC BY 4.0 with a link back

CVE-2026-94439 · Severity: high · CVSS 7.5 · Published 2026-10-08

Go's HTTP server contains a connection desynchronization flaw when responding to CONNECT requests with a 2xx status code. An intermediate proxy treating the connection as a tunnel while the server continues to parse HTTP requests could enable request smuggling attacks, potentially allowing an attacker to inject or misdirect requests through the compromised connection.

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

## Quick answers

**Is CVE-2026-94439 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-94439 being exploited in the wild.

**How severe is CVE-2026-94439?** High severity, with a CVSS score of 7.5, published 8 October 2026.

**Which products and versions are affected?** go (Go) prior to fix; stdlib (Go) SEMVER:introduced=0,fixed=1.26.9,introduced=1.27.0-0,fixed=1.27.2.

**Is there a fix for CVE-2026-94439?** Yes. stdlib (Go): upgrade to 1.27.2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-94439 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-94439?** Check whether you run go (Go) or 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 1.27.2 or later

  ```sh
  go get stdlib@v1.27.2
  ```


## Technical details

The vulnerability occurs in net/http when an HTTP/1 server handler sends a 2xx response to a CONNECT request and returns without hijacking the connection; the server improperly continues parsing HTTP requests on what should become a tunnel. This connection state desynchronization between client, proxy, and server enables HTTP request smuggling, where attackers exploit differing interpretations of the connection protocol. The fix closes the connection unconditionally after any CONNECT response.

## Affected products

- Go Go prior to fix

## Identifiers

- CVE-2026-94439
- GO-2026-6613

## Timeline

- 2026-10-08: disclosed
- 2026-10-08: advisory

## References

- [https://go.dev/cl/847311](https://go.dev/cl/847311)
- [https://go.dev/issue/81744](https://go.dev/issue/81744)

## Related threats

- [Go HTTP/1 server race condition in MaxBytesReader header handling](https://junglewise.ai/threats/cve-2026-97054-for-http-1-servers-when-maxbytesreader-s-limit-is-exceeded)
- [Go command unsafe pkg-config flag handling in cgo](https://junglewise.ai/threats/cve-2026-97039-building-a-malicious-package-that-uses-cgo-pkg-config-directives)
- [Go linker code injection via malicious package compilation](https://junglewise.ai/threats/cve-2026-97038-building-a-malicious-package-containing-syso-files-or-cgo-linker)
- [Go arbitrary code execution via malicious cgo linker flags](https://junglewise.ai/threats/cve-2026-97037-building-a-malicious-package-that-uses-cgo-could-cause-arbitrary)
- [Go cgo arbitrary code execution via Apple linker argument injection](https://junglewise.ai/threats/cve-2026-97036-on-darwin-building-a-malicious-package-that-uses-cgo-could-cause)