CVE-2021-47590

Local task hang via recursive subflow socket locking

Published Jun 19, 2024 · Updated May 11, 2026

Improper locking in Linux kernel 5.13 through 5.15.10 allows local users to hang an MPTCP sending task during socket option synchronization. __mptcp_push_pending() calls mptcp_flush_join_list() while holding the subflow socket lock, and the resulting synchronization path attempts to acquire that lock again. The condition requires local access and an MPTCP send path that flushes the join list and synchronizes socket options; the demonstrated consequence is an uninterruptible task hang.

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

What happened

Improper locking in Linux kernel 5.13 through 5.15.10 allows local users to hang an MPTCP sending task during socket option synchronization. __mptcp_push_pending() calls mptcp_flush_join_list() while holding the subflow socket lock, and the resulting synchronization path attempts to acquire that lock again. The condition requires local access and an MPTCP send path that flushes the join list and synchronizes socket options; the demonstrated consequence is an uninterruptible task hang.

The record

CVE
CVE-2021-47590
Published
Jun 19, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-667, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 19, 2024CVE publishedPublication date reported by the CVE source.
  2. May 11, 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=1b3e7ede1365a24db1b4fd837e58a595f52fa4ad <23311b92755ffa9087332d1bb8c71c0f6a10cc08
  2. Affected versionversion=1b3e7ede1365a24db1b4fd837e58a595f52fa4ad <3d79e3756ca90f7a6087b77b62c1d9c0801e0820
  3. Affected versionversion=5.13

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1b3e7ede1365a24db1b4fd837e58a595f52fa4ad <23311b92755ffa9087332d1bb8c71c0f6a10cc08; version=1b3e7ede1365a24db1b4fd837e58a595f52fa4ad <3d79e3756ca90f7a6087b77b62c1d9c0801e0820; version=5.13

Published CVSS scores

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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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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-667Improper Locking
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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