High severity · published Aug 13, 2026
CVE-2026-56853
Apply ReadHeaderTimeout when doing unencrypted HTTP/2 check in net/http
7.5
CVSS
0.6%
EPSS
No
On KEV
Description
When a server is configured to support unencrypted HTTP/2, it reads a few bytes from each new connection to see if they contain the HTTP/2 client preface. ReadHeaderTimeout is unexpectedly not being applied when doing this.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 47% 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 1.25.13; 1.26.0-0 before 1.26.6; 1.27.0-0 before 1.27.0-rc.3 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-56853
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-56853
go.dev
https://go.dev/cl/795540
go.dev
https://go.dev/issue/80205
groups.google.com
https://groups.google.com/g/golang-announce/c/94pEornpRlI
pkg.go.dev
https://pkg.go.dev/vuln/GO-2026-6089
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