CVE-2021-47587

Network traffic disruption via unsynchronized descriptor writes

Published Jun 19, 2024 · Updated Aug 5, 2026

Improper locking in Linux kernel SYSTEMPORT drivers allows local users to disrupt network traffic through concurrent transmit queues. The transmit path serializes descriptors only within each queue, so concurrent writes to WRITE_PORT_HI and WRITE_PORT_LO let hardware pair length or status data with the wrong packet buffer. Reaching the flaw requires Broadcom SYSTEMPORT hardware and multiple active transmit queues; affected UDP and TCP packets can carry incorrect lengths despite valid checksums.

CVSS severity5.5
Medium
EPSS probability0.55%
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 SYSTEMPORT drivers allows local users to disrupt network traffic through concurrent transmit queues. The transmit path serializes descriptors only within each queue, so concurrent writes to WRITE_PORT_HI and WRITE_PORT_LO let hardware pair length or status data with the wrong packet buffer. Reaching the flaw requires Broadcom SYSTEMPORT hardware and multiple active transmit queues; affected UDP and TCP packets can carry incorrect lengths despite valid checksums.

The record

CVE
CVE-2021-47587
Published
Jun 19, 2024
Updated
Aug 5, 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. 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=3.16
  2. Affected versionversion=80105befdb4b8cea924711b40b2462b87df65b62 <595a684fa6f23b21958379a18cfa83862c73c2e1
  3. Affected versionversion=80105befdb4b8cea924711b40b2462b87df65b62 <6e1011cd183faae8daff275c72444edcdfe0d473
  4. Affected versionversion=80105befdb4b8cea924711b40b2462b87df65b62 <8b8e6e782456f1ce02a7ae914bbd5b1053f0b034
  5. Affected versionversion=80105befdb4b8cea924711b40b2462b87df65b62 <8ed2f5d08d6e59f8c78b2869bfb95d0be32c094c
  6. Affected versionversion=80105befdb4b8cea924711b40b2462b87df65b62 <c675256a7f131f5ba3f331efb715e8f31ea0e392
  7. Affected versionversion=80105befdb4b8cea924711b40b2462b87df65b62 <de57f62f76450b934de8203711bdc4f7953c3421
  8. Affected versionversion=80105befdb4b8cea924711b40b2462b87df65b62 <eb4687c7442942e115420a30185f8d83faf37696
  9. Affected versionversion=80105befdb4b8cea924711b40b2462b87df65b62 <f3fde37d3f0d429f0fcce214cb52588a9e21260e

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=3.16; version=80105befdb4b8cea924711b40b2462b87df65b62 <595a684fa6f23b21958379a18cfa83862c73c2e1; version=80105befdb4b8cea924711b40b2462b87df65b62 <6e1011cd183faae8daff275c72444edcdfe0d473; version=80105befdb4b8cea924711b40b2462b87df65b62 <8b8e6e782456f1ce02a7ae914bbd5b1053f0b034; version=80105befdb4b8cea924711b40b2462b87df65b62 <8ed2f5d08d6e59f8c78b2869bfb95d0be32c094c; version=80105befdb4b8cea924711b40b2462b87df65b62 <c675256a7f131f5ba3f331efb715e8f31ea0e392; version=80105befdb4b8cea924711b40b2462b87df65b62 <de57f62f76450b934de8203711bdc4f7953c3421; version=80105befdb4b8cea924711b40b2462b87df65b62 <eb4687c7442942e115420a30185f8d83faf37696; version=80105befdb4b8cea924711b40b2462b87df65b62 <f3fde37d3f0d429f0fcce214cb52588a9e21260e

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

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-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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