FKIE_CVE-2026-78660
Vulnerability from fkie_nvd - Published: 2026-10-08 23:17 - Updated: 2026-10-09 17:16
Severity
Summary
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.
References
Impacted products
| Vendor | Product | Version |
|---|
{
"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": "security@golang.org"
}
],
"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": "2026-10-09T17:16:49.243",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 7.5,
"baseSeverity": "HIGH",
"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:N",
"version": "3.1"
},
"exploitabilityScore": 3.9,
"impactScore": 3.6,
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-78660",
"options": [
{
"exploitation": "none"
},
{
"automatable": "yes"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-09T16:21:51.217328Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-10-08T23:17:03.510",
"references": [
{
"source": "security@golang.org",
"url": "https://go.dev/cl/835145"
},
{
"source": "security@golang.org",
"url": "https://go.dev/cl/836385"
},
{
"source": "security@golang.org",
"url": "https://go.dev/issue/81115"
},
{
"source": "security@golang.org",
"url": "https://groups.google.com/g/golang-announce/c/U2fTuyDJznI"
},
{
"source": "security@golang.org",
"url": "https://pkg.go.dev/vuln/GO-2026-6610"
}
],
"sourceIdentifier": "security@golang.org",
"vulnStatus": "Awaiting Analysis",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-444"
}
],
"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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