CVE-2026-78663

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.

CVSS v3 9.1 CRITICAL

9.1^/10

CVSS v3 : CRITICAL

Vector :

Exploitability : 3.9 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://go.dev/cl/847187
https://go.dev/cl/847310
https://go.dev/issue/81743
https://groups.google.com/g/golang-announce/c/U2fTuyDJznI
https://groups.google.com/g/golang-announce/c/ZPwCyRUuGBs
https://pkg.go.dev/vuln/GO-2026-6612

Configurations

No configuration.

History

09 Oct 2026, 17:16

Type	Values Removed	Values Added
CVSS	v2 : ~~unknown~~ v3 : ~~unknown~~	v2 : unknown v3 : 9.1
CWE		CWE-675

08 Oct 2026, 23:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-10-08 23:17

Updated : 2026-10-09 17:16

NVD link : CVE-2026-78663

Mitre link : CVE-2026-78663

CVE.ORG link : CVE-2026-78663

JSON object : View

Products Affected

No product.

CWE

CWE-675

Multiple Operations on Resource in Single-Operation Context

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"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": 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{"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": 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"https://groups.google.com/g/golang-announce/c/ZPwCyRUuGBs", "source": "security@golang.org"}, {"url": "https://pkg.go.dev/vuln/GO-2026-6612", "source": "security@golang.org"}], "vulnStatus": "Awaiting Analysis", "weaknesses": [{"type": "Secondary", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "description": [{"lang": "en", "value": "CWE-675"}]}], "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."}], "lastModified": "2026-10-09T17:16:49.420", "sourceIdentifier": "security@golang.org"}