CVE-2021-47293

Packet corruption via Ethernet-only skbmod handling

Published May 21, 2024 · Updated May 11, 2026

Improper packet handling in the Linux kernel allows local users to corrupt non-Ethernet traffic by applying an skbmod action. The tcf_skbmod_act() path in net/sched/act_skbmod.c treats every packet as Ethernet and rewrites link-layer header fields without first checking its protocol. Reaching the flaw requires permission to install traffic-control qdiscs and filters on an interface, and affected traffic is silently corrupted rather than disclosed or executed.

CVSS severity7.8
High
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper packet handling in the Linux kernel allows local users to corrupt non-Ethernet traffic by applying an skbmod action. The tcf_skbmod_act() path in net/sched/act_skbmod.c treats every packet as Ethernet and rewrites link-layer header fields without first checking its protocol. Reaching the flaw requires permission to install traffic-control qdiscs and filters on an interface, and affected traffic is silently corrupted rather than disclosed or executed.

The record

CVE
CVE-2021-47293
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1565.002
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. May 21, 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=4.9
  2. Affected versionversion=86da71b57383d40993cb90baafb3735cffe5d800 <071729150be9e1d1b851b70efb6d91ee9269d57b
  3. Affected versionversion=86da71b57383d40993cb90baafb3735cffe5d800 <34f1e1f657fae2891b485a3b2b95fe4d2aef9f0d
  4. Affected versionversion=86da71b57383d40993cb90baafb3735cffe5d800 <727d6a8b7ef3d25080fad228b2c4a1d4da5999c6
  5. Affected versionversion=86da71b57383d40993cb90baafb3735cffe5d800 <a88414fb1117f2fe65fb88e45ba694e1d09d5024
  6. Affected versionversion=86da71b57383d40993cb90baafb3735cffe5d800 <e4fdca366806f6bab374d1a95e626a10a3854b0c

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linuxversion=4.9; version=86da71b57383d40993cb90baafb3735cffe5d800 <071729150be9e1d1b851b70efb6d91ee9269d57b; version=86da71b57383d40993cb90baafb3735cffe5d800 <34f1e1f657fae2891b485a3b2b95fe4d2aef9f0d; version=86da71b57383d40993cb90baafb3735cffe5d800 <727d6a8b7ef3d25080fad228b2c4a1d4da5999c6; version=86da71b57383d40993cb90baafb3735cffe5d800 <a88414fb1117f2fe65fb88e45ba694e1d09d5024; version=86da71b57383d40993cb90baafb3735cffe5d800 <e4fdca366806f6bab374d1a95e626a10a3854b0c

Published CVSS scores

7.8NIST NVDCVSS: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

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

Weakness, pattern, technique

T1565.002Transmitted Data Manipulation

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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