FKIE_CVE-2026-78663
Vulnerability from fkie_nvd - Published: 2026-10-08 23:17 - Updated: 2026-10-09 17:16
Severity
Summary
The HTTP/2 server can refund connection-level flow control twice for the same data: Once when a client resets a stream (refunding data for any sent-but-unread portion of the stream), and again when a request handler reads the buffered data. A malicious client can exploit this to bypass the configured connection-level flow control limit (MaxReceiveBufferPerConnection). Total buffered data is still limited by the concurrent stream limit and stream-level flow control.
References
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"collectionURL": "https://pkg.go.dev",
"defaultStatus": "unaffected",
"packageName": "net/http",
"product": "net/http",
"programRoutines": [
{
"name": "http2requestBody.Close"
},
{
"name": "http2requestBody.Read"
},
{
"name": "http2serverConn.closeStream"
},
{
"name": "http2serverConn.handlerDone"
},
{
"name": "http2serverConn.newWriterAndRequest"
},
{
"name": "http2serverConn.newWriterAndRequestNoBody"
},
{
"name": "http2serverConn.noteBodyRead"
},
{
"name": "http2serverConn.processHeaders"
},
{
"name": "http2serverConn.runHandler"
},
{
"name": "http2serverConn.scheduleHandler"
},
{
"name": "CanonicalHeaderKey"
},
{
"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": "Cookie.String"
},
{
"name": "Cookie.Valid"
},
{
"name": "CrossOriginProtection.AddInsecureBypassPattern"
},
{
"name": "CrossOriginProtection.AddTrustedOrigin"
},
{
"name": "CrossOriginProtection.Check"
},
{
"name": "Dir.Open"
},
{
"name": "Error"
},
{
"name": "Get"
},
{
"name": "Handle"
},
{
"name": "HandleFunc"
},
{
"name": "HandlerFunc.ServeHTTP"
},
{
"name": "Head"
},
{
"name": "Header.Add"
},
{
"name": "Header.Del"
},
{
"name": "Header.Get"
},
{
"name": "Header.Set"
},
{
"name": "Header.Values"
},
{
"name": "Header.Write"
},
{
"name": "Header.WriteSubset"
},
{
"name": "ListenAndServe"
},
{
"name": "ListenAndServeTLS"
},
{
"name": "NewRequest"
},
{
"name": "NewRequestWithContext"
},
{
"name": "NotFound"
},
{
"name": "ParseCookie"
},
{
"name": "ParseSetCookie"
},
{
"name": "ParseTime"
},
{
"name": "Post"
},
{
"name": "PostForm"
},
{
"name": "ProxyFromEnvironment"
},
{
"name": "ReadRequest"
},
{
"name": "ReadResponse"
},
{
"name": "Redirect"
},
{
"name": "Request.AddCookie"
},
{
"name": "Request.BasicAuth"
},
{
"name": "Request.Cookie"
},
{
"name": "Request.Cookies"
},
{
"name": "Request.CookiesNamed"
},
{
"name": "Request.FormFile"
},
{
"name": "Request.FormValue"
},
{
"name": "Request.MultipartReader"
},
{
"name": "Request.ParseForm"
},
{
"name": "Request.ParseMultipartForm"
},
{
"name": "Request.PostFormValue"
},
{
"name": "Request.Referer"
},
{
"name": "Request.SetBasicAuth"
},
{
"name": "Request.UserAgent"
},
{
"name": "Request.Write"
},
{
"name": "Request.WriteProxy"
},
{
"name": "Response.Cookies"
},
{
"name": "Response.Location"
},
{
"name": "Response.Write"
},
{
"name": "ResponseController.EnableFullDuplex"
},
{
"name": "ResponseController.Flush"
},
{
"name": "ResponseController.Hijack"
},
{
"name": "ResponseController.SetReadDeadline"
},
{
"name": "ResponseController.SetWriteDeadline"
},
{
"name": "Serve"
},
{
"name": "ServeContent"
},
{
"name": "ServeFile"
},
{
"name": "ServeFileFS"
},
{
"name": "ServeMux.Handle"
},
{
"name": "ServeMux.HandleFunc"
},
{
"name": "ServeMux.ServeHTTP"
},
{
"name": "ServeTLS"
},
{
"name": "Server.Close"
},
{
"name": "Server.ListenAndServe"
},
{
"name": "Server.ListenAndServeTLS"
},
{
"name": "Server.Serve"
},
{
"name": "Server.ServeTLS"
},
{
"name": "Server.SetKeepAlivesEnabled"
},
{
"name": "Server.Shutdown"
},
{
"name": "SetCookie"
},
{
"name": "Transport.CancelRequest"
},
{
"name": "Transport.Clone"
},
{
"name": "Transport.CloseIdleConnections"
},
{
"name": "Transport.NewClientConn"
},
{
"name": "Transport.RoundTrip"
},
{
"name": "body.Close"
},
{
"name": "body.Read"
},
{
"name": "bodyEOFSignal.Close"
},
{
"name": "bodyEOFSignal.Read"
},
{
"name": "bodyLocked.Read"
},
{
"name": "bufioFlushWriter.Write"
},
{
"name": "cancelTimerBody.Close"
},
{
"name": "cancelTimerBody.Read"
},
{
"name": "checkConnErrorWriter.Write"
},
{
"name": "chunkWriter.Write"
},
{
"name": "connReader.Read"
},
{
"name": "connectMethodKey.String"
},
{
"name": "expectContinueReader.Close"
},
{
"name": "expectContinueReader.Read"
},
{
"name": "extraHeader.Write"
},
{
"name": "fileHandler.ServeHTTP"
},
{
"name": "fileTransport.RoundTrip"
},
{
"name": "globalOptionsHandler.ServeHTTP"
},
{
"name": "gzipReader.Close"
},
{
"name": "gzipReader.Read"
},
{
"name": "http1ClientConn.Close"
},
{
"name": "http1ClientConn.RoundTrip"
},
{
"name": "http2ClientConn.Close"
},
{
"name": "http2ClientConn.Ping"
},
{
"name": "http2ClientConn.RoundTrip"
},
{
"name": "http2ClientConn.Shutdown"
},
{
"name": "http2ConnectionError.Error"
},
{
"name": "http2ErrCode.String"
},
{
"name": "http2FrameHeader.String"
},
{
"name": "http2FrameType.String"
},
{
"name": "http2FrameWriteRequest.String"
},
{
"name": "http2Framer.ReadFrame"
},
{
"name": "http2Framer.ReadFrameForHeader"
},
{
"name": "http2Framer.ReadFrameHeader"
},
{
"name": "http2Framer.WriteContinuation"
},
{
"name": "http2Framer.WriteData"
},
{
"name": "http2Framer.WriteDataPadded"
},
{
"name": "http2Framer.WriteGoAway"
},
{
"name": "http2Framer.WriteHeaders"
},
{
"name": "http2Framer.WritePing"
},
{
"name": "http2Framer.WritePriority"
},
{
"name": "http2Framer.WritePushPromise"
},
{
"name": "http2Framer.WriteRSTStream"
},
{
"name": "http2Framer.WriteRawFrame"
},
{
"name": "http2Framer.WriteSettings"
},
{
"name": "http2Framer.WriteSettingsAck"
},
{
"name": "http2Framer.WriteWindowUpdate"
},
{
"name": "http2GoAwayError.Error"
},
{
"name": "http2Server.ServeConn"
},
{
"name": "http2Setting.String"
},
{
"name": "http2SettingID.String"
},
{
"name": "http2SettingsFrame.ForeachSetting"
},
{
"name": "http2StreamError.Error"
},
{
"name": "http2Transport.CloseIdleConnections"
},
{
"name": "http2Transport.NewClientConn"
},
{
"name": "http2Transport.RoundTrip"
},
{
"name": "http2Transport.RoundTripOpt"
},
{
"name": "http2bufferedWriter.Flush"
},
{
"name": "http2bufferedWriter.Write"
},
{
"name": "http2bufferedWriterTimeoutWriter.Write"
},
{
"name": "http2chunkWriter.Write"
},
{
"name": "http2clientConnPool.GetClientConn"
},
{
"name": "http2connError.Error"
},
{
"name": "http2dataBuffer.Read"
},
{
"name": "http2duplicatePseudoHeaderError.Error"
},
{
"name": "http2gzipReader.Close"
},
{
"name": "http2gzipReader.Read"
},
{
"name": "http2headerFieldNameError.Error"
},
{
"name": "http2headerFieldValueError.Error"
},
{
"name": "http2netHTTPClientConn.Close"
},
{
"name": "http2netHTTPClientConn.RoundTrip"
},
{
"name": "http2noDialClientConnPool.GetClientConn"
},
{
"name": "http2noDialH2RoundTripper.NewClientConn"
},
{
"name": "http2noDialH2RoundTripper.RoundTrip"
},
{
"name": "http2pipe.Read"
},
{
"name": "http2priorityWriteSchedulerRFC7540.CloseStream"
},
{
"name": "http2priorityWriteSchedulerRFC7540.OpenStream"
},
{
"name": "http2priorityWriteSchedulerRFC9218.OpenStream"
},
{
"name": "http2pseudoHeaderError.Error"
},
{
"name": "http2responseWriter.Flush"
},
{
"name": "http2responseWriter.FlushError"
},
{
"name": "http2responseWriter.Push"
},
{
"name": "http2responseWriter.SetReadDeadline"
},
{
"name": "http2responseWriter.SetWriteDeadline"
},
{
"name": "http2responseWriter.Write"
},
{
"name": "http2responseWriter.WriteHeader"
},
{
"name": "http2responseWriter.WriteString"
},
{
"name": "http2roundRobinWriteScheduler.OpenStream"
},
{
"name": "http2serverConn.CloseConn"
},
{
"name": "http2serverConn.Flush"
},
{
"name": "http2stickyErrWriter.Write"
},
{
"name": "http2transportResponseBody.Close"
},
{
"name": "http2transportResponseBody.Read"
},
{
"name": "http2unencryptedTransport.RoundTrip"
},
{
"name": "http2writeData.String"
},
{
"name": "initALPNRequest.ServeHTTP"
},
{
"name": "loggingConn.Close"
},
{
"name": "loggingConn.Read"
},
{
"name": "loggingConn.Write"
},
{
"name": "maxBytesReader.Close"
},
{
"name": "maxBytesReader.Read"
},
{
"name": "onceCloseListener.Close"
},
{
"name": "persistConn.Read"
},
{
"name": "persistConnWriter.ReadFrom"
},
{
"name": "persistConnWriter.Write"
},
{
"name": "populateResponse.Write"
},
{
"name": "populateResponse.WriteHeader"
},
{
"name": "readTrackingBody.Close"
},
{
"name": "readTrackingBody.Read"
},
{
"name": "readWriteCloserBody.CloseWrite"
},
{
"name": "readWriteCloserBody.Read"
},
{
"name": "redirectHandler.ServeHTTP"
},
{
"name": "response.Flush"
},
{
"name": "response.FlushError"
},
{
"name": "response.Hijack"
},
{
"name": "response.ReadFrom"
},
{
"name": "response.Write"
},
{
"name": "response.WriteHeader"
},
{
"name": "response.WriteString"
},
{
"name": "serverHandler.ServeHTTP"
},
{
"name": "socksDialer.DialWithConn"
},
{
"name": "socksUsernamePassword.Authenticate"
},
{
"name": "stringWriter.WriteString"
},
{
"name": "timeoutHandler.ServeHTTP"
},
{
"name": "timeoutWriter.Write"
},
{
"name": "timeoutWriter.WriteHeader"
},
{
"name": "transportReadFromServerError.Error"
},
{
"name": "unencryptedHTTP2Request.ServeHTTP"
}
],
"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": "requestBody.Close"
},
{
"name": "requestBody.Read"
},
{
"name": "serverConn.closeStream"
},
{
"name": "serverConn.handlerDone"
},
{
"name": "serverConn.newWriterAndRequest"
},
{
"name": "serverConn.newWriterAndRequestNoBody"
},
{
"name": "serverConn.noteBodyRead"
},
{
"name": "serverConn.processHeaders"
},
{
"name": "serverConn.runHandler"
},
{
"name": "serverConn.scheduleHandler"
},
{
"name": "Server.ServeConn"
}
],
"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": "requestBody.Close"
},
{
"name": "requestBody.Read"
},
{
"name": "serverConn.closeStream"
},
{
"name": "serverConn.handlerDone"
},
{
"name": "serverConn.newWriterAndRequest"
},
{
"name": "serverConn.newWriterAndRequestNoBody"
},
{
"name": "serverConn.noteBodyRead"
},
{
"name": "serverConn.processHeaders"
},
{
"name": "serverConn.runHandler"
},
{
"name": "serverConn.scheduleHandler"
},
{
"name": "ClientConn.Close"
},
{
"name": "ClientConn.Ping"
},
{
"name": "ClientConn.RoundTrip"
},
{
"name": "ClientConn.Shutdown"
},
{
"name": "ConfigureServer"
},
{
"name": "ConfigureTransport"
},
{
"name": "ConfigureTransports"
},
{
"name": "ConnectionError.Error"
},
{
"name": "ErrCode.String"
},
{
"name": "FrameHeader.String"
},
{
"name": "FrameType.String"
},
{
"name": "FrameWriteRequest.String"
},
{
"name": "Framer.ReadFrame"
},
{
"name": "Framer.ReadFrameForHeader"
},
{
"name": "Framer.ReadFrameHeader"
},
{
"name": "Framer.WriteContinuation"
},
{
"name": "Framer.WriteData"
},
{
"name": "Framer.WriteDataPadded"
},
{
"name": "Framer.WriteGoAway"
},
{
"name": "Framer.WriteHeaders"
},
{
"name": "Framer.WritePing"
},
{
"name": "Framer.WritePriority"
},
{
"name": "Framer.WritePriorityUpdate"
},
{
"name": "Framer.WritePushPromise"
},
{
"name": "Framer.WriteRSTStream"
},
{
"name": "Framer.WriteRawFrame"
},
{
"name": "Framer.WriteSettings"
},
{
"name": "Framer.WriteSettingsAck"
},
{
"name": "Framer.WriteWindowUpdate"
},
{
"name": "GoAwayError.Error"
},
{
"name": "ReadFrameHeader"
},
{
"name": "Server.ServeConn"
},
{
"name": "Setting.String"
},
{
"name": "SettingID.String"
},
{
"name": "SettingsFrame.ForeachSetting"
},
{
"name": "StreamError.Error"
},
{
"name": "Transport.CloseIdleConnections"
},
{
"name": "Transport.NewClientConn"
},
{
"name": "Transport.RoundTrip"
},
{
"name": "Transport.RoundTripOpt"
},
{
"name": "bufferedWriter.Flush"
},
{
"name": "bufferedWriter.Write"
},
{
"name": "bufferedWriterTimeoutWriter.Write"
},
{
"name": "chunkWriter.Write"
},
{
"name": "clientConnPool.GetClientConn"
},
{
"name": "connError.Error"
},
{
"name": "dataBuffer.Read"
},
{
"name": "duplicatePseudoHeaderError.Error"
},
{
"name": "gzipReader.Close"
},
{
"name": "gzipReader.Read"
},
{
"name": "headerFieldNameError.Error"
},
{
"name": "headerFieldValueError.Error"
},
{
"name": "netHTTPClientConn.Close"
},
{
"name": "netHTTPClientConn.RoundTrip"
},
{
"name": "noDialClientConnPool.GetClientConn"
},
{
"name": "noDialH2RoundTripper.NewClientConn"
},
{
"name": "noDialH2RoundTripper.RoundTrip"
},
{
"name": "pipe.Read"
},
{
"name": "priorityWriteSchedulerRFC7540.CloseStream"
},
{
"name": "priorityWriteSchedulerRFC7540.OpenStream"
},
{
"name": "priorityWriteSchedulerRFC9218.OpenStream"
},
{
"name": "pseudoHeaderError.Error"
},
{
"name": "responseWriter.Flush"
},
{
"name": "responseWriter.FlushError"
},
{
"name": "responseWriter.Push"
},
{
"name": "responseWriter.SetReadDeadline"
},
{
"name": "responseWriter.SetWriteDeadline"
},
{
"name": "responseWriter.Write"
},
{
"name": "responseWriter.WriteHeader"
},
{
"name": "responseWriter.WriteString"
},
{
"name": "roundRobinWriteScheduler.OpenStream"
},
{
"name": "serverConn.CloseConn"
},
{
"name": "serverConn.Flush"
},
{
"name": "stickyErrWriter.Write"
},
{
"name": "transportResponseBody.Close"
},
{
"name": "transportResponseBody.Read"
},
{
"name": "unencryptedTransport.RoundTrip"
},
{
"name": "writeData.String"
}
],
"vendor": "golang.org/x/net",
"versions": [
{
"lessThan": "0.60.0",
"status": "affected",
"version": "0",
"versionType": "semver"
}
]
}
],
"source": "security@golang.org"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "The HTTP/2 server can refund connection-level flow control twice for the same data: Once when a client resets a stream (refunding data for any sent-but-unread portion of the stream), and again when a request handler reads the buffered data. A malicious client can exploit this to bypass the configured connection-level flow control limit (MaxReceiveBufferPerConnection). Total buffered data is still limited by the concurrent stream limit and stream-level flow control."
}
],
"id": "CVE-2026-78663",
"lastModified": "2026-10-09T17:16:49.420",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 9.1,
"baseSeverity": "CRITICAL",
"confidentialityImpact": "NONE",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 3.9,
"impactScore": 5.2,
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-78663",
"options": [
{
"exploitation": "none"
},
{
"automatable": "yes"
},
{
"technicalImpact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-09T16:40:08.220862Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-10-08T23:17:03.647",
"references": [
{
"source": "security@golang.org",
"url": "https://go.dev/cl/847187"
},
{
"source": "security@golang.org",
"url": "https://go.dev/cl/847310"
},
{
"source": "security@golang.org",
"url": "https://go.dev/issue/81743"
},
{
"source": "security@golang.org",
"url": "https://groups.google.com/g/golang-announce/c/U2fTuyDJznI"
},
{
"source": "security@golang.org",
"url": "https://groups.google.com/g/golang-announce/c/ZPwCyRUuGBs"
},
{
"source": "security@golang.org",
"url": "https://pkg.go.dev/vuln/GO-2026-6612"
}
],
"sourceIdentifier": "security@golang.org",
"vulnStatus": "Awaiting Analysis",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-675"
}
],
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"type": "Secondary"
}
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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