CVE-2026-78663
Status: Awaiting AnalysisCritical (9.1)—
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
- Version: 3.1
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
- Base score: 9.1
Exploitation probability (EPSS)
- Probability of exploitation in the next 30 days: 0.57%
- Percentile among all scored CVEs: 46
- Score date: 10/14/2026
EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).
🎯 ATT&CK techniques
How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.
- Exploitation
T1190Exploit Public-Facing Applicationinitial access85 % - Primary impact
T1499.004Application or System Exploitationimpact75 %
Vulnerabilidad en servidor HTTP/2 accesible por red sin autenticación (AV:N/PR:N). Explotación remota del control de flujo permite DoS por saturación de buffer y corrupción de datos en tránsito.
Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.
🛡️ ATT&CK mitigations that cover these techniques
CWEs
- CWE-675
References
Raw JSON (NVD)
Show
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"name": "Request.FormFile"
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"name": "requestBody.Close"
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{
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"name": "FrameHeader.String"
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{
"name": "FrameType.String"
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{
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{
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{
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"name": "GoAwayError.Error"
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{
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"name": "SettingID.String"
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"name": "StreamError.Error"
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{
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{
"name": "headerFieldNameError.Error"
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"name": "headerFieldValueError.Error"
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{
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{
"name": "noDialH2RoundTripper.RoundTrip"
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{
"name": "pipe.Read"
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{
"name": "priorityWriteSchedulerRFC7540.CloseStream"
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{
"name": "priorityWriteSchedulerRFC7540.OpenStream"
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{
"name": "priorityWriteSchedulerRFC9218.OpenStream"
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{
"name": "pseudoHeaderError.Error"
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{
"name": "responseWriter.Flush"
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"name": "responseWriter.FlushError"
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"name": "responseWriter.SetReadDeadline"
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"name": "responseWriter.SetWriteDeadline"
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"name": "responseWriter.Write"
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{
"name": "responseWriter.WriteHeader"
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"name": "responseWriter.WriteString"
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"name": "roundRobinWriteScheduler.OpenStream"
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{
"name": "serverConn.CloseConn"
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{
"name": "serverConn.Flush"
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{
"name": "stickyErrWriter.Write"
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{
"name": "transportResponseBody.Close"
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{
"name": "transportResponseBody.Read"
},
{
"name": "unencryptedTransport.RoundTrip"
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{
"name": "writeData.String"
}
]
}
]
}
],
"published": "2026-10-08T23:17:03.647",
"references": [
{
"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",
"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"
}