CVE-2021-47222

Kernel memory corruption via stale tunnel destination

Published May 21, 2024 · Updated Aug 5, 2026

Use-after-free in Linux kernel bridge VLAN tunneling allows local users to corrupt memory by triggering egress on a stale destination. br_handle_egress_vlan_tunnel assigns the result of dst_clone even when the destination has a zero reference count or was deleted, instead of acquiring it safely. Reaching the flaw requires local low-privileged access and bridge VLAN-tunnel egress; the resulting stale reference causes kernel warnings, reference underflow, and memory corruption.

CVSS severity7.8
High
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Linux kernel bridge VLAN tunneling allows local users to corrupt memory by triggering egress on a stale destination. br_handle_egress_vlan_tunnel assigns the result of dst_clone even when the destination has a zero reference count or was deleted, instead of acquiring it safely. Reaching the flaw requires local low-privileged access and bridge VLAN-tunnel egress; the resulting stale reference causes kernel warnings, reference underflow, and memory corruption.

The record

CVE
CVE-2021-47222
Published
May 21, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=11538d039ac6efcf4f1a6c536e1b87cd3668a9fd <25053a8404ba17ca48f5553d487afc1882e9f56c
  2. Affected versionversion=11538d039ac6efcf4f1a6c536e1b87cd3668a9fd <42020f7f37a90d24b9551f5f7eba3f7c7c102968
  3. Affected versionversion=11538d039ac6efcf4f1a6c536e1b87cd3668a9fd <79855be6445b6592bddb7bd7167083ec8cdbd73f
  4. Affected versionversion=11538d039ac6efcf4f1a6c536e1b87cd3668a9fd <84fc1c944e45ab317e2e70a0e7f76fa2a5e43b6e
  5. Affected versionversion=11538d039ac6efcf4f1a6c536e1b87cd3668a9fd <cfc579f9d89af4ada58c69b03bcaa4887840f3b3
  6. Affected versionversion=11538d039ac6efcf4f1a6c536e1b87cd3668a9fd <fc7fdd8c5c2ad2fe3e297698be9d4dbe4a4e0579
  7. Affected versionversion=4.11

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=11538d039ac6efcf4f1a6c536e1b87cd3668a9fd <25053a8404ba17ca48f5553d487afc1882e9f56c; version=11538d039ac6efcf4f1a6c536e1b87cd3668a9fd <42020f7f37a90d24b9551f5f7eba3f7c7c102968; version=11538d039ac6efcf4f1a6c536e1b87cd3668a9fd <79855be6445b6592bddb7bd7167083ec8cdbd73f; version=11538d039ac6efcf4f1a6c536e1b87cd3668a9fd <84fc1c944e45ab317e2e70a0e7f76fa2a5e43b6e; version=11538d039ac6efcf4f1a6c536e1b87cd3668a9fd <cfc579f9d89af4ada58c69b03bcaa4887840f3b3; version=11538d039ac6efcf4f1a6c536e1b87cd3668a9fd <fc7fdd8c5c2ad2fe3e297698be9d4dbe4a4e0579; version=4.11

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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