HTTP/1 server connection desynchronization after 2xx CONNECT response in net/http
What to do
Vendor fix available. Upgrade each affected package to the fixed version on its release line (stdlib 1.27.2, 1.26.9), redeploy, then verify what is actually installed.
This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.
Affected packages
Go stdlib
- Affected
- < 1.26.9>= 1.27.0-0, < 1.27.2
- Fixed in
- 1.26.9, 1.27.2
Sources
- Open Source Vulnerabilities (OSV.dev), including the GitHub Advisory Database
OSV record GO-2026-6613 lists affected ranges: Go stdlib >=0 =1.27.0-0 <1.27.2 (fixed)
VerifiedObserved Structured OSV record; not marked as GitHub-reviewed.
Severity and exploitation
- Exploitation
- No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
- CVSS
- not scored
- EPSS
- CVE-2026-94439: 0.41% estimated exploitation activity in the next 30 days; percentile 35.81 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description
As published by the source; long descriptions are shortened.
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.
Dates and revisions
- Published by the source
- Last modified by the source
- Source last checked
- Revision 1 · created ·
Published from osv record GO-2026-6613
Agent brief
Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.
# Patch Next advisory brief: CVE-2026-94439 Advisory: HTTP/1 server connection desynchronization after 2xx CONNECT response in net/http IDs: CVE-2026-94439 Record: https://patchnext.com/advisories/cve-2026-94439 (revision 1, source checked 23 Oct 2026, 22:04 UTC) Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected. Severity: Unrated Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV. Vendor response: Vendor fix available; fixed versions by package: stdlib 1.27.2, 1.26.9. A vendor fix does not mean a deployment is fixed. ## Affected components - Go stdlib: affected < 1.26.9; >= 1.27.0-0, < 1.27.2; fixed in 1.26.9, 1.27.2 ## Suggested inspection (read-only) - Go stdlib: check the installed version with your package manager. ## Supported action Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version. ## Required regression checks - Run the test suite and a production build. - Exercise the features that depend on stdlib. - Repeat the inspection and confirm that only fixed versions remain installed. ## Rollback considerations - Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward. ## Unresolved questions - Which deployments run an affected version? - Exploitation status can change. Check again before lowering the priority. - Mark the work resolved only after the fixed version is verified in production. ## Sources - Verified: https://osv.dev/vulnerability/GO-2026-6613 (OSV record GO-2026-6613 lists affected ranges: Go stdlib >=0 =1.27.0-0 <1.27.2 (fixed)) Commands are suggestions: review each one before running it.
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