CVE-2021-47561

Local privilege escalation via virtio-I2C use-after-free

Published May 24, 2024 · Updated Aug 5, 2026

Use-after-free in the virtio-I2C driver in Linux 5.15 through 5.15.5 allows local users to corrupt guest kernel memory via I2C ioctls. The virtio_i2c_xfer timeout path frees request buffers while the backend can still access them, allowing later device writes into reused memory. Access to a virtio-I2C /dev/i2c-* device is required; successful exploitation can disclose or modify kernel memory, escalate privileges, or crash the guest.

CVSS severity7.8
High
EPSS probability0.20%
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 the virtio-I2C driver in Linux 5.15 through 5.15.5 allows local users to corrupt guest kernel memory via I2C ioctls. The virtio_i2c_xfer timeout path frees request buffers while the backend can still access them, allowing later device writes into reused memory. Access to a virtio-I2C /dev/i2c-* device is required; successful exploitation can disclose or modify kernel memory, escalate privileges, or crash the guest.

The record

CVE
CVE-2021-47561
Published
May 24, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 24, 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=3cfc88380413d20f777dc6648a38f683962e52bf <84e1d0bf1d7121759622dabf8fbef4c99ad597c5
  2. Affected versionversion=3cfc88380413d20f777dc6648a38f683962e52bf <cc432b0727ce404cc13e8f6b5ce29f412c3f9f1f
  3. Affected versionversion=5.15

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=3cfc88380413d20f777dc6648a38f683962e52bf <84e1d0bf1d7121759622dabf8fbef4c99ad597c5; version=3cfc88380413d20f777dc6648a38f683962e52bf <cc432b0727ce404cc13e8f6b5ce29f412c3f9f1f; version=5.15

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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

T1068Exploitation for Privilege Escalation

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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