CVE-2026-56853

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

HIGH

7.5

CVSS Score

Published: August 13, 2026 at 09:58 PM UTC

Updated: September 3, 2026 at 04:54 PM UTC

1 product affected across 1 vendor.NET

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Severity

HIGH7.5

Exploit prediction

EPSS 0.6%

SSVC

No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

.NET · Go Standard Librarygo

60%

v < 1.25.131.26.0-0 ≤ v < 1.26.61.27.0-0 ≤ v < 1.27.0-rc.31.26.0-0 1.27.0-0

Affected range stops below 1.25.13, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.26.6, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.27.0-rc.3, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (4)

Source: cverecord

https://go.dev/issue/80205

Source: cverecord

https://go.dev/cl/795540

Source: cverecord

https://groups.google.com/g/golang-announce/c/94pEornpRlI

Source: cverecord

https://pkg.go.dev/vuln/GO-2026-6089

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGHCISA-ADP

Attack Vector: NETWORK
Complexity: LOW
Privileges: NONE
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: NONE
Integrity: NONE
Availability: HIGH

Vector?

Quick Info

StatusAWAITING ANALYSIS

CWE

CWE-770

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