CVE-2021-47010Public exploit

Host-wide policy modification via non-namespaced flag write

Published Feb 28, 2024 · Updated May 11, 2026

Improper namespace isolation in Linux kernel 4.15 allows local users to alter a host-wide TCP congestion-control policy. In tcp_set_default_congestion_control(), the code marks a restricted algorithm TCP_CONG_NON_RESTRICTED through a global ca->flags field rather than namespace-scoped state. A local user able to set the default algorithm inside a non-initial network namespace can thereby change the host-wide read-only allowed-congestion-control list.

CVSS severity7.8
High
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper namespace isolation in Linux kernel 4.15 allows local users to alter a host-wide TCP congestion-control policy. In tcp_set_default_congestion_control(), the code marks a restricted algorithm TCP_CONG_NON_RESTRICTED through a global ca->flags field rather than namespace-scoped state. A local user able to set the default algorithm inside a non-initial network namespace can thereby change the host-wide read-only allowed-congestion-control list.

The record

CVE
CVE-2021-47010
Published
Feb 28, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-400, T1611
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 28, 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=4.15
  2. Affected versionversion=6670e152447732ba90626f36dfc015a13fbf150e <6c1ea8bee75df8fe2184a50fcd0f70bf82986f42
  3. Affected versionversion=6670e152447732ba90626f36dfc015a13fbf150e <8d432592f30fcc34ef5a10aac4887b4897884493
  4. Affected versionversion=6670e152447732ba90626f36dfc015a13fbf150e <9884f745108f7d25b189bbcd6754e284fb29ab68
  5. Affected versionversion=6670e152447732ba90626f36dfc015a13fbf150e <992de06308d9a9584d59b96d294ac676f924e437
  6. Affected versionversion=6670e152447732ba90626f36dfc015a13fbf150e <e7d7bedd507bb732e600403b7a96f9fe48d0ca31
  7. Affected versionversion=6670e152447732ba90626f36dfc015a13fbf150e <efe1532a6e1a8e3c343d04fff510f0ed80328f9c

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4.15; version=6670e152447732ba90626f36dfc015a13fbf150e <6c1ea8bee75df8fe2184a50fcd0f70bf82986f42; version=6670e152447732ba90626f36dfc015a13fbf150e <8d432592f30fcc34ef5a10aac4887b4897884493; version=6670e152447732ba90626f36dfc015a13fbf150e <9884f745108f7d25b189bbcd6754e284fb29ab68; version=6670e152447732ba90626f36dfc015a13fbf150e <992de06308d9a9584d59b96d294ac676f924e437; version=6670e152447732ba90626f36dfc015a13fbf150e <e7d7bedd507bb732e600403b7a96f9fe48d0ca31; version=6670e152447732ba90626f36dfc015a13fbf150e <efe1532a6e1a8e3c343d04fff510f0ed80328f9c
The Linux Kernel Organization · Linux Kernelversion=4.15; version=6670e1524477 <6c1ea8bee75d; version=6670e1524477 <8d432592f30f; version=6670e1524477 <9884f745108f; version=6670e1524477 <992de06308d9; version=6670e1524477 <e7d7bedd507b; version=6670e1524477 <efe1532a6e1a

Published CVSS scores

3.3SUSECVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
7.8CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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 exploitPublished

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1611Escape to Host

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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