CVE-2021-47448Network attack vector

Denial of service via uncleared MPTCP readiness flag

Published May 22, 2024 · Updated Aug 5, 2026

Denial of service in Linux kernel 5.6 through 5.14.13 allows remote attackers to cause an RCU stall through partial MPTCP data. The mptcp_recvmsg path leaves MPTCP_DATA_READY set when MSG_WAITALL cannot be satisfied, so mptcp_wait_data returns without sleeping and loops indefinitely. An exposed MPTCP listener using MSG_WAITALL is required; a peer can stop sending after partial data, consuming CPU and starving RCU processing.

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 5.6 through 5.14.13 allows remote attackers to cause an RCU stall through partial MPTCP data. The mptcp_recvmsg path leaves MPTCP_DATA_READY set when MSG_WAITALL cannot be satisfied, so mptcp_wait_data returns without sleeping and loops indefinitely. An exposed MPTCP listener using MSG_WAITALL is required; a peer can stop sending after partial data, consuming CPU and starving RCU processing.

The record

CVE
CVE-2021-47448
Published
May 22, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-835, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 22, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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=5.6
  2. Affected versionversion=7a6a6cbc3e592e339ad23e4e8ede9a3f6160bda8 <1a4554e94f0deff9fc1dc5addf93fa579cc29711
  3. Affected versionversion=7a6a6cbc3e592e339ad23e4e8ede9a3f6160bda8 <612f71d7328c14369924384ad2170aae2a6abd92

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.6; version=7a6a6cbc3e592e339ad23e4e8ede9a3f6160bda8 <1a4554e94f0deff9fc1dc5addf93fa579cc29711; version=7a6a6cbc3e592e339ad23e4e8ede9a3f6160bda8 <612f71d7328c14369924384ad2170aae2a6abd92

Published CVSS scores

5.5NIST National Vulnerability DatabaseCVSS: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

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499.004Application or System Exploitation

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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