CVE-2021-47111

Guest-triggered dom0 crash via stale RX thread pointer

Published Mar 15, 2024 · Updated Aug 5, 2026

Use-after-free in Linux xen-netback allows guest OS users to crash dom0 via a malformed packet from a PV network frontend. During backend teardown, kthread_stop is called through a stale RX-task pointer because no task reference was retained after the queue-0 thread exited. Exploitation requires control of a guest PV network frontend; a malformed packet terminates the thread, and subsequent backend destruction triggers the host crash.

CVSS severity8.8
High
EPSS probability0.24%
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 xen-netback allows guest OS users to crash dom0 via a malformed packet from a PV network frontend. During backend teardown, kthread_stop is called through a stale RX-task pointer because no task reference was retained after the queue-0 thread exited. Exploitation requires control of a guest PV network frontend; a malformed packet terminates the thread, and subsequent backend destruction triggers the host crash.

The record

CVE
CVE-2021-47111
Published
Mar 15, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 15, 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=2ac061ce97f413bfbbdd768f7d2e0fda2e8170df <107866a8eb0b664675a260f1ba0655010fac1e08
  2. Affected versionversion=2ac061ce97f413bfbbdd768f7d2e0fda2e8170df <6b53db8c4c14b4e7256f058d202908b54a7b85b4
  3. Affected versionversion=2ac061ce97f413bfbbdd768f7d2e0fda2e8170df <caec9bcaeb1a5f03f2d406305355c853af10c13e
  4. Affected versionversion=5.5

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2ac061ce97f413bfbbdd768f7d2e0fda2e8170df <107866a8eb0b664675a260f1ba0655010fac1e08; version=2ac061ce97f413bfbbdd768f7d2e0fda2e8170df <6b53db8c4c14b4e7256f058d202908b54a7b85b4; version=2ac061ce97f413bfbbdd768f7d2e0fda2e8170df <caec9bcaeb1a5f03f2d406305355c853af10c13e; version=5.5

Published CVSS scores

4.4Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
8.8Linux kernel CVE teamCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
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
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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