CVE-2021-23134

Privilege escalation via stale NFC LLCP pointer

Published May 12, 2021 · Updated Sep 17, 2024

Use-after-free in Linux Kernel NFC LLCP sockets before 5.12.4 allows local users to elevate privileges by binding two sockets. llcp_sock_bind and llcp_sock_connect can assign one local object to two sockets, then release it without clearing llcp_sock->local, leaving a stale pointer used during closure. Typical configurations require CAP_NET_RAW; successful exploitation grants kernel-level privileges and can also crash the host.

CVSS severity7.8
High
EPSS probability0.37%
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 NFC LLCP sockets before 5.12.4 allows local users to elevate privileges by binding two sockets. llcp_sock_bind and llcp_sock_connect can assign one local object to two sockets, then release it without clearing llcp_sock->local, leaving a stale pointer used during closure. Typical configurations require CAP_NET_RAW; successful exploitation grants kernel-level privileges and can also crash the host.

The record

CVE
CVE-2021-23134
Published
May 12, 2021
Updated
Sep 17, 2024
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-416, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 12, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 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?

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  1. Affected versionversion=unspecified <5.12.4

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=unspecified <5.12.4

Published CVSS scores

4.6NVDAV:L/AC:L/Au:N/C:P/I:P/A:P
7.8SUSECVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8Palo Alto Networks CNACVSS: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
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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