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CVE-2026-80634VulnerabilityPublished Updated

Microsoft · netfilter: flowtable: avoid num_encaps underflow on bridge VLAN untag

Affects MicrosoftSource GCVE Database

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Authoritative record:CVE-2026-80634· Critical 9.8

Not known to be exploited · CVSS 9.8 Critical · fixed in ee8440bb000fff4ef8acbfc99652851e9ca0a35b : patch Microsoft as a priority.

Data as of 7 Nov 2026, 12:18 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (Linux)CVSS 3.19.8
Patch
Available – fixed in ee8440bb000fff4ef8acbfc99652851e9ca0a35b, e052f920773b73be49eb4d8702a9f85de7464363, 547ea9f567498e4accc89e7816264f15a1a0629f +3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 28 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: 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 7 Nov 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ e990cef6516daa4e1e236433579e333f74fd38cb, < ee8440bb000fff4ef8acbfc99652851e9ca0a35b
Fixed in
  • ee8440bb000fff4ef8acbfc99652851e9ca0a35b
LinuxLinuxAffected
  • ≥ e990cef6516daa4e1e236433579e333f74fd38cb, < e052f920773b73be49eb4d8702a9f85de7464363
Fixed in
  • e052f920773b73be49eb4d8702a9f85de7464363
LinuxLinuxAffected
  • ≥ e990cef6516daa4e1e236433579e333f74fd38cb, < 547ea9f567498e4accc89e7816264f15a1a0629f
Fixed in
  • 547ea9f567498e4accc89e7816264f15a1a0629f
LinuxLinuxAffected
  • ≥ e990cef6516daa4e1e236433579e333f74fd38cb, < 9a4e3a9017ba3da2de187b72ed6545641a0d0a84
Fixed in
  • 9a4e3a9017ba3da2de187b72ed6545641a0d0a84
LinuxLinuxAffected
  • ≥ e990cef6516daa4e1e236433579e333f74fd38cb, < 2f55fa28011c97d6495d5787808db10a8c2d690d
Fixed in
  • 2f55fa28011c97d6495d5787808db10a8c2d690d
LinuxLinuxAffected
  • ≥ e990cef6516daa4e1e236433579e333f74fd38cb, < 1b52aeb40c9f04bf50eeb4ea09142139d163e239
Fixed in
  • 1b52aeb40c9f04bf50eeb4ea09142139d163e239

Description

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

References

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