HTTP/1 server connection desynchronization after 2xx CONNECT response in net/http (Go standard library net/http)
At a glance
- Source
- NVD
- EPSS
- EPSS 0.41 % · percentile 36 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- Go
- NVD status
- Awaiting Analysis
Description
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.
Weaknesses (CWE)
- CWE-444 — Inconsistent Interpretation of HTTP Requests
References
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N | CISA-ADP |
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N | NVD · 134c704f-9b21-4f2e-91b3-4a467353bcc0 (Secondary) |
Advisories
- GO-2026-6613 — HTTP/1 server connection desynchronization after 2xx CONNECT response in net/http
European references
- ENISA EUVD · EUVD-2026-95428
- GCVE · GCVE-0-2026-94439
CERT-FR advisories
- CERTFR-2026-AVI-1385 — Multiples vulnérabilités dans les produits VMware · cert.ssi.gouv.fr
Affected products
| Product | Versions |
|---|---|
| Go standard library · net/http | affected 0 < 1.26.9 ; affected 1.27.0-0 < 1.27.2 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |