CVE-2026-94439 (GCVE-0-2026-94439)
Vulnerability from cvelistv5 – Published: 2026-10-08 22:53 – Updated: 2026-10-09 16:52
VLAI
EPSS
VEX
Title
HTTP/1 server connection desynchronization after 2xx CONNECT response in net/http
Summary
When an HTTP server handler sends a 2xx response to an HTTP/1 CONNECT request and returns without hijacking the connection, the server improperly continues to read and serve requests from the connection. Since a 2xx response to an HTTP/1 CONNECT converts the connection into a tunnel, the server should not treat the connection as continuing to contain HTTP. The impact of this misbehavior is mostly limited to potential request smuggling, where an intermediate proxy considers the data on the connection to be tunneled and the server considers it to be HTTP.
Severity
7.5 (High)
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-09 16:45 UTC
CWE
- CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Assigner
References
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Go standard library | net/http |
Affected:
0 , < 1.26.9
(semver)
Affected: 1.27.0-0 , < 1.27.2 (semver) |
guessed |
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}
],
"id": "CVE-2026-94439",
"lastModified": "2026-10-09T17:16:50.703",
"metrics": {
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"confidentialityImpact": "HIGH",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
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"timestamp": "2026-10-09T16:45:53.919403Z",
"version": "2.0.3"
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"published": "2026-10-08T23:17:04.760",
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{
"source": "security@golang.org",
"url": "https://go.dev/issue/81744"
},
{
"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-2026-6613"
}
],
"sourceIdentifier": "security@golang.org",
"vulnStatus": "Awaiting Analysis",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-444"
}
],
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"type": "Secondary"
}
]
}
},
"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-10-08T23:53:34+00:00",
"cve": "CVE-2026-94439",
"id": "CVE-2026-94439",
"initial_release_date": "2026-10-08T22:53:59.976000+00:00",
"product_status:known_affected": "341",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "net/http: golang: net/http: HTTP request smuggling via improper handling of HTTP/1 CONNECT responses",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-94439.json",
"version": "3"
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 7.5,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
"version": "3.1"
}
},
{
"other": {
"content": {
"id": "CVE-2026-94439",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "yes"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-09T16:45:53.919403Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-444",
"description": "CWE-444 Inconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027)",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-09T16:43:46.124Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://pkg.go.dev",
"defaultStatus": "unaffected",
"packageName": "net/http",
"product": "net/http",
"programRoutines": [
{
"name": "chunkWriter.writeHeader"
},
{
"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.RoundTrip"
},
{
"name": "http2Handler.ServeHTTP"
},
{
"name": "http2ResponseWriter.Flush"
},
{
"name": "http2ResponseWriter.FlushError"
},
{
"name": "http2ResponseWriter.Push"
},
{
"name": "http2RoundTripper.RoundTrip"
},
{
"name": "http3ServerHandler.ServeHTTP"
},
{
"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"
},
{
"lessThan": "1.27.2",
"status": "affected",
"version": "1.27.0-0",
"versionType": "semver"
}
]
}
],
"credits": [
{
"lang": "en",
"value": "Jakub Ciolek (https://ciolek.dev)"
}
],
"descriptions": [
{
"lang": "en",
"value": "When an HTTP server handler sends a 2xx response to an HTTP/1 CONNECT request and returns without hijacking the connection, the server improperly continues to read and serve requests from the connection. Since a 2xx response to an HTTP/1 CONNECT converts the connection into a tunnel, the server should not treat the connection as continuing to contain HTTP. The impact of this misbehavior is mostly limited to potential request smuggling, where an intermediate proxy considers the data on the connection to be tunneled and the server considers it to be HTTP."
}
],
"problemTypes": [
{
"descriptions": [
{
"description": "CWE-444: Inconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027)",
"lang": "en"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-08T22:53:59.976Z",
"orgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
"shortName": "Go"
},
"references": [
{
"url": "https://go.dev/cl/847311"
},
{
"url": "https://go.dev/issue/81744"
},
{
"url": "https://groups.google.com/g/golang-announce/c/U2fTuyDJznI"
},
{
"url": "https://pkg.go.dev/vuln/GO-2026-6613"
}
],
"title": "HTTP/1 server connection desynchronization after 2xx CONNECT response in net/http"
}
},
"cveMetadata": {
"assignerOrgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
"assignerShortName": "Go",
"cveId": "CVE-2026-94439",
"datePublished": "2026-10-08T22:53:59.976Z",
"dateReserved": "2026-09-21T16:43:04.757Z",
"dateUpdated": "2026-10-09T16:52:15.154Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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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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