CVE-2026-78660 - Vulnerability Details - OpenCVE

Historically, we have been rather lax about malformed framing-related headers in our HTTP/2 implementation, as they cannot interfere with HTTP/2 framing. However, this makes it possible for our HTTP/2 implementation to forward responses containing such headers to an HTTP/1 client when acting as a reverse proxy. If the HTTP/1 client also does not behave strictly enough, this can result in response smuggling.

No CVSS v4.0

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

No data.

No data.

No data.

OpenCVE Enrichment is a feature of OpenCVE that uses AI to automatically link vendors and products to CVEs. Learn more on GitHub.

No data.

Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References

Link	Providers
https://go.dev/cl/835145
https://go.dev/cl/836385
https://go.dev/issue/81115
https://groups.google.com/g/golang-announce/c/U2fTuyDJznI
https://pkg.go.dev/vuln/GO-2026-6610

History

Fri, 09 Oct 2026 02:15:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-20

Thu, 08 Oct 2026 23:00:00 +0000

Type	Values Removed	Values Added
Description		Historically, we have been rather lax about malformed framing-related headers in our HTTP/2 implementation, as they cannot interfere with HTTP/2 framing. However, this makes it possible for our HTTP/2 implementation to forward responses containing such headers to an HTTP/1 client when acting as a reverse proxy. If the HTTP/1 client also does not behave strictly enough, this can result in response smuggling.
Title		HTTP/2 transport accepts malformed framing-related headers in net/http
References		https://go.dev/cl/835145 https://go.dev/cl/836385 https://go.dev/issue/81115 https://groups.google.com/g/golang-announce/c/U2fTuyDJznI https://pkg.go.dev/vuln/GO-2026-6610

Projects

Sign in to view the affected projects.

MITRE

Status: PUBLISHED

Assigner: Go

Published: 2026-10-08T22:53:59.334Z

Updated: 2026-10-08T22:53:59.334Z

Reserved: 2026-08-24T23:36:15.738Z

Link: CVE-2026-78660

Vulnrichment

No data.

NVD

Status : Received

Published: 2026-10-08T23:17:03.510

Modified: 2026-10-08T23:17:03.510

Link: CVE-2026-78660

Redhat

No data.

OpenCVE Enrichment

Updated: 2026-10-09T02:00:23Z

Weaknesses

CWE-20

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-78660", "assignerOrgId": "1bb62c36-49e3-4200-9d77-64a1400537cc", "state": "PUBLISHED", "assignerShortName": "Go", "dateReserved": "2026-08-24T23:36:15.738Z", "datePublished": "2026-10-08T22:53:59.334Z", "dateUpdated": "2026-10-08T22:53:59.334Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "1bb62c36-49e3-4200-9d77-64a1400537cc", "shortName": "Go", "dateUpdated": "2026-10-08T22:53:59.334Z"}, "title": "HTTP/2 transport accepts malformed framing-related headers in net/http", "descriptions": [{"lang": "en", "value": "Historically, we have been rather lax about malformed framing-related headers in our HTTP/2 implementation, as they cannot interfere with HTTP/2 framing. However, this makes it possible for our HTTP/2 implementation to forward responses containing such headers to an HTTP/1 client when acting as a reverse proxy. If the HTTP/1 client also does not behave strictly enough, this can result in response smuggling."}], "affected": [{"vendor": "Go standard library", "product": "net/http", "collectionURL": "https://pkg.go.dev", "packageName": "net/http", "versions": [{"version": "0", "lessThan": "1.26.9", "status": "affected", "versionType": "semver"}], "programRoutines": [{"name": "http2clientConnReadLoop.handleResponse"}, {"name": "Client.CloseIdleConnections"}, {"name": "Client.Do"}, {"name": "Client.Get"}, {"name": "Client.Head"}, {"name": "Client.Post"}, {"name": "Client.PostForm"}, {"name": "ClientConn.Close"}, {"name": "ClientConn.RoundTrip"}, {"name": "Get"}, {"name": "Head"}, {"name": "Post"}, {"name": "PostForm"}, {"name": "Transport.CloseIdleConnections"}, {"name": "Transport.NewClientConn"}, {"name": "Transport.RoundTrip"}, {"name": "http1ClientConn.Close"}, {"name": "http1ClientConn.RoundTrip"}, {"name": "http2Transport.NewClientConn"}, {"name": "http2Transport.RoundTrip"}, {"name": "http2Transport.RoundTripOpt"}, {"name": "http2clientConnPool.GetClientConn"}, {"name": "http2noDialClientConnPool.GetClientConn"}, {"name": "http2noDialH2RoundTripper.NewClientConn"}, {"name": "http2noDialH2RoundTripper.RoundTrip"}, {"name": "http2unencryptedTransport.RoundTrip"}], "defaultStatus": "unaffected"}, {"vendor": "Go standard library", "product": "net/http/internal/http2", "collectionURL": "https://pkg.go.dev", "packageName": "net/http/internal/http2", "versions": [{"version": "1.27.0-0", "lessThan": "1.27.2", "status": "affected", "versionType": "semver"}], "programRoutines": [{"name": "clientConnReadLoop.handleResponse"}, {"name": "Transport.AddConn"}, {"name": "Transport.NewClientConn"}, {"name": "Transport.RoundTrip"}, {"name": "Transport.RoundTripOpt"}, {"name": "clientConnPool.GetClientConn"}, {"name": "noDialClientConnPool.GetClientConn"}], "defaultStatus": "unaffected"}, {"vendor": "golang.org/x/net", "product": "golang.org/x/net/http2", "collectionURL": "https://pkg.go.dev", "packageName": "golang.org/x/net/http2", "versions": [{"version": "0", "lessThan": "0.60.0", "status": "affected", "versionType": "semver"}], "programRoutines": [{"name": "clientConnReadLoop.handleResponse"}, {"name": "Transport.NewClientConn"}, {"name": "Transport.RoundTrip"}, {"name": "Transport.RoundTripOpt"}, {"name": "clientConnPool.GetClientConn"}, {"name": "noDialClientConnPool.GetClientConn"}, {"name": "noDialH2RoundTripper.NewClientConn"}, {"name": "noDialH2RoundTripper.RoundTrip"}, {"name": "unencryptedTransport.RoundTrip"}], "defaultStatus": "unaffected"}], "problemTypes": [{"descriptions": [{"lang": "en", "description": "CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')"}]}], "references": [{"url": "https://go.dev/cl/835145"}, {"url": "https://go.dev/cl/836385"}, {"url": "https://go.dev/issue/81115"}, {"url": "https://groups.google.com/g/golang-announce/c/U2fTuyDJznI"}, {"url": "https://pkg.go.dev/vuln/GO-2026-6610"}], "credits": [{"lang": "en", "value": "TJ Barton"}]}}}

{"affected": [{"affectedData": [{"collectionURL": "https://pkg.go.dev", "defaultStatus": "unaffected", "packageName": "net/http", "product": "net/http", "programRoutines": [{"name": "http2clientConnReadLoop.handleResponse"}, {"name": "Client.CloseIdleConnections"}, {"name": "Client.Do"}, {"name": "Client.Get"}, {"name": "Client.Head"}, {"name": "Client.Post"}, {"name": "Client.PostForm"}, {"name": "ClientConn.Close"}, {"name": "ClientConn.RoundTrip"}, {"name": "Get"}, {"name": "Head"}, {"name": "Post"}, {"name": "PostForm"}, {"name": "Transport.CloseIdleConnections"}, {"name": "Transport.NewClientConn"}, {"name": "Transport.RoundTrip"}, {"name": "http1ClientConn.Close"}, {"name": "http1ClientConn.RoundTrip"}, {"name": "http2Transport.NewClientConn"}, {"name": "http2Transport.RoundTrip"}, {"name": "http2Transport.RoundTripOpt"}, {"name": "http2clientConnPool.GetClientConn"}, {"name": "http2noDialClientConnPool.GetClientConn"}, {"name": "http2noDialH2RoundTripper.NewClientConn"}, {"name": "http2noDialH2RoundTripper.RoundTrip"}, {"name": "http2unencryptedTransport.RoundTrip"}], "vendor": "Go standard library", "versions": [{"lessThan": "1.26.9", "status": "affected", "version": "0", "versionType": "semver"}]}, {"collectionURL": "https://pkg.go.dev", "defaultStatus": "unaffected", "packageName": "net/http/internal/http2", "product": "net/http/internal/http2", "programRoutines": [{"name": "clientConnReadLoop.handleResponse"}, {"name": "Transport.AddConn"}, {"name": "Transport.NewClientConn"}, {"name": "Transport.RoundTrip"}, {"name": "Transport.RoundTripOpt"}, {"name": "clientConnPool.GetClientConn"}, {"name": "noDialClientConnPool.GetClientConn"}], "vendor": "Go standard library", "versions": [{"lessThan": "1.27.2", "status": "affected", "version": "1.27.0-0", "versionType": "semver"}]}, {"collectionURL": "https://pkg.go.dev", "defaultStatus": "unaffected", "packageName": "golang.org/x/net/http2", "product": "golang.org/x/net/http2", "programRoutines": [{"name": "clientConnReadLoop.handleResponse"}, {"name": "Transport.NewClientConn"}, {"name": "Transport.RoundTrip"}, {"name": "Transport.RoundTripOpt"}, {"name": "clientConnPool.GetClientConn"}, {"name": "noDialClientConnPool.GetClientConn"}, {"name": "noDialH2RoundTripper.NewClientConn"}, {"name": "noDialH2RoundTripper.RoundTrip"}, {"name": "unencryptedTransport.RoundTrip"}], "vendor": "golang.org/x/net", "versions": [{"lessThan": "0.60.0", "status": "affected", "version": "0", "versionType": "semver"}]}], "source": "[email protected]"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Historically, we have been rather lax about malformed framing-related headers in our HTTP/2 implementation, as they cannot interfere with HTTP/2 framing. However, this makes it possible for our HTTP/2 implementation to forward responses containing such headers to an HTTP/1 client when acting as a reverse proxy. If the HTTP/1 client also does not behave strictly enough, this can result in response smuggling."}], "id": "CVE-2026-78660", "lastModified": "2026-10-08T23:17:03.510", "metrics": {}, "published": "2026-10-08T23:17:03.510", "references": [{"source": "[email protected]", "url": "https://go.dev/cl/835145"}, {"source": "[email protected]", "url": "https://go.dev/cl/836385"}, {"source": "[email protected]", "url": "https://go.dev/issue/81115"}, {"source": "[email protected]", "url": "https://groups.google.com/g/golang-announce/c/U2fTuyDJznI"}, {"source": "[email protected]", "url": "https://pkg.go.dev/vuln/GO-2026-6610"}], "sourceIdentifier": "[email protected]", "vulnStatus": "Received"}