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CVE-2026-78663VulnerabilityPublished Updated

Microsoft · Double flow control refund on HTTP/2 server streams in net/http

Affects MicrosoftSource GCVE Database

0
Authoritative record:CVE-2026-78663· Critical 9.1

Not known to be exploited · CVSS 9.1 Critical · fixed in 1.26.9 : patch Microsoft as a priority.

Data as of 28 Oct 2026, 08:43 UTC

CVSS 3.1 base score
9.1Critical
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 1.26.9, 1.27.2, 0.60.0
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 8 Oct 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade net/http to 1.26.9; net/http/internal/http2 to 1.27.2; golang.org/x/net/http2 to 0.60.0.

Affected software

ProductAffectedFixed in
Go standard librarynet/httpAffected
  • <1.26.9
Fixed in
  • 1.26.9
Go standard librarynet/http/internal/http2Affected
  • >=1.27.0-0 <1.27.2
Fixed in
  • 1.27.2
golang.org/x/netgolang.org/x/net/http2Affected
  • <0.60.0
Fixed in
  • 0.60.0
Gonet/httppkg:golang/net/httpOther threatsAffected
  • <1.26.9
Fixed in
  • 1.26.9
Gonet/http/internal/http2pkg:golang/net/http/internal/http2Other threatsAffected
  • >=1.27.0-0 <1.27.2
Fixed in
  • 1.27.2
Gogolang.org/x/net/http2pkg:golang/golang.org/x/net/http2Other threatsAffected
  • <0.60.0
Fixed in
  • 0.60.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle

References

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