High severity · published Oct 8, 2026
CVE-2026-94439
HTTP/1 server connection desynchronization after 2xx CONNECT response in net/http
7.5
CVSS
0.4%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 36% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NE
net/http · Go standard library
before 1.26.9; 1.27.0-0 before 1.27.2 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-94439
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-94439
go.dev
https://go.dev/cl/847311
go.dev
https://go.dev/issue/81744
groups.google.com
https://groups.google.com/g/golang-announce/c/U2fTuyDJznI
pkg.go.dev
https://pkg.go.dev/vuln/GO-2026-6613
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