CVE-2026-94439 PUBLISHED

HTTP/1 server connection desynchronization after 2xx CONNECT response in net/http

Assigner: Go
Reserved: 21.09.2026 Published: 08.10.2026 Updated: 08.10.2026

When an HTTP server handler sends a 2xx response to an HTTP/1 CONNECT request and returns without hijacking the connection, the server improperly continues to read and serve requests from the connection. Since a 2xx response to an HTTP/1 CONNECT converts the connection into a tunnel, the server should not treat the connection as continuing to contain HTTP. The impact of this misbehavior is mostly limited to potential request smuggling, where an intermediate proxy considers the data on the connection to be tunneled and the server considers it to be HTTP.

Product Status

Vendor Go standard library
Product net/http
Versions Default: unaffected
  • affected from 0 to 1.26.9 (excl.)
  • affected from 1.27.0-0 to 1.27.2 (excl.)

Credits

  • Jakub Ciolek (https://ciolek.dev)

References

Problem Types

  • CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')