CVE-2021-34981

Kernel code execution via double-freed socket file

Published May 7, 2024 · Updated Aug 4, 2024

Double free in the CMTP module in Linux Kernel 4.15.0-118-generic allows local users to execute code in the kernel context. When cmtp_attach_device fails after cmtp_add_connection starts the session thread, the caller and thread each release the same socket file reference. Exploitation requires CAP_NET_ADMIN in the initial namespace and a failed CAPI hardware attachment; successful exploitation grants kernel-context code execution.

CVSS severity7.5
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

Double free in the CMTP module in Linux Kernel 4.15.0-118-generic allows local users to execute code in the kernel context. When cmtp_attach_device fails after cmtp_add_connection starts the session thread, the caller and thread each release the same socket file reference. Exploitation requires CAP_NET_ADMIN in the initial namespace and a failed CAPI hardware attachment; successful exploitation grants kernel-context code execution.

The record

CVE
CVE-2021-34981
Published
May 7, 2024
Updated
Aug 4, 2024
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-415, T1068
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. May 7, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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?

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

  1. Affected versionversion=4.15.0-118-generic

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linux Kernelversion=4.15.0-118-generic

Published CVSS scores

6.7NIST NVDCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
7.5Zero Day InitiativeCVSS:3.0/AV:L/AC:H/PR:H/UI:N/S:C/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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-415Double Free
T1068Exploitation for Privilege Escalation

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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