CVE-2021-29266

Local system crash via stale eventfd reference

Published Mar 26, 2021 · Updated Aug 3, 2024

Use-after-free in Linux kernel 5.8 through 5.10.25 and 5.11 through 5.11.8 allows local users to crash the system. vhost_vdpa_config_put releases the config_ctx eventfd reference without clearing the pointer, so reopening the same vhost-vDPA character device releases the stale reference again and underflows its reference count. Exploitation requires local write access to a /dev/vhost-vdpa-* device; the demonstrated consequence is a kernel fault and system crash.

CVSS severity7.8
High
EPSS probability0.32%
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 5.8 through 5.10.25 and 5.11 through 5.11.8 allows local users to crash the system. vhost_vdpa_config_put releases the config_ctx eventfd reference without clearing the pointer, so reopening the same vhost-vDPA character device releases the stale reference again and underflows its reference count. Exploitation requires local write access to a /dev/vhost-vdpa-* device; the demonstrated consequence is a kernel fault and system crash.

The record

CVE
CVE-2021-29266
Published
Mar 26, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-416, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 26, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.4SUSECVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.2NIST NVDAV:L/AC:L/Au:N/C:C/I:C/A:C

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

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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