CVE-2020-25673Public exploit

Local system hang via repeated LLCP socket connects

Published May 26, 2021 · Updated Aug 4, 2024

Denial of service in Linux kernel NFC LLCP allows local users to hang the system by repeatedly connecting a nonblocking socket. llcp_sock_connect() relinks a socket already in LLCP_CONNECTING state, making its connecting-list node point to itself and causing an endless loop. Exploitation requires local access to create an NFC LLCP socket; the bounded consequence is a system-wide service hang.

CVSS severity5.5
Medium
EPSS probability0.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Linux kernel NFC LLCP allows local users to hang the system by repeatedly connecting a nonblocking socket. llcp_sock_connect() relinks a socket already in LLCP_CONNECTING state, making its connecting-list node point to itself and causing an endless loop. Exploitation requires local access to create an NFC LLCP socket; the bounded consequence is a system-wide service hang.

The record

CVE
CVE-2020-25673
Published
May 26, 2021
Updated
Aug 4, 2024
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-400, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 26, 2021CVE 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?

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  1. Affected versionversion=All

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=All

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.9NIST NVDAV:L/AC:L/Au:N/C:N/I:N/A:C

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499Endpoint Denial of Service

Public exploit references

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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