CVE-2026-56853

Apply ReadHeaderTimeout when doing unencrypted HTTP/2 check in net/http

Published Aug 13, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Weaknesses CWE-770
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Go Standard Library
Go Standard Library net/http
Vendors & Products Go Standard Library
Go Standard Library net/http
Type Values Removed Values Added
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.
Title Apply ReadHeaderTimeout when doing unencrypted HTTP/2 check in net/http
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Go
Published
Updated
Aug 14, 2026, 3:23 PM
Reserved
Jun 23, 2026, 3:10 PM
Status
Awaiting Analysis
Published
Aug 13, 2026, 10:17 PM
Modified
Sep 3, 2026, 4:37 PM
Severity
Important
Public date
Aug 13, 2026, 9:58 PM