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CVE Record

CVE-2021-47293: net/sched: act_skbmod: Skip non-Ethernet packets

In the Linux kernel, the following vulnerability has been resolved: net/sched: act_skbmod: Skip non-Ethernet packets Currently tcf_skbmod_act() assumes that packets use Ethernet as their L2 protocol, which is not always the case. As an example, for CAN devices: $ ip link add dev vcan0 type vcan $ ip link set up vcan0 $ tc qdisc add dev vcan0 root handle 1: htb $ tc filter add dev vcan0 parent 1: protocol ip prio 10 \ matchall action skbmod swap mac Doing the above silently corrupts all the packets. Do not perform skbmod actions for non-Ethernet packets.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue can silently corrupt traffic when a packet-modification feature is applied to non-Ethernet traffic, such as CAN. The source does not show remote code execution, privilege escalation, or active exploitation. Business urgency depends on whether affected kernels are used in environments relying on non-Ethernet interfaces and Linux traffic control packet modification.

Executive priority

Handle as targeted operational risk, not a broad emergency, unless your environment uses Linux traffic control on CAN or other non-Ethernet networks. Prioritize affected industrial, embedded, or vehicle-adjacent systems where silent packet corruption could disrupt operations.

Technical view

CVE-2021-47293 affects Linux kernel act_skbmod. The tcf_skbmod_act() path assumed Ethernet Layer 2 headers and could corrupt packets on non-Ethernet devices. The resolved behavior skips skbmod actions for non-Ethernet packets. Public data provides no CVSS, CWE, or exploitation evidence.

Likely exposure

Most exposed systems are Linux hosts using affected kernel versions with traffic control skbmod actions on non-Ethernet interfaces, especially CAN. General Linux servers without this traffic-control configuration appear less likely to be affected based on the source bundle.

Exploitation context

The source describes packet corruption triggered by a specific local traffic-control configuration. It does not cite public exploitation, CISA KEV listing, remote attack paths, or weaponized use. Treat exploitation status as not evidenced, not impossible.

Researcher notes

The evidence is narrow: affected Linux kernel behavior, non-Ethernet packet corruption, and upstream stable commits. No CVSS or CWE is supplied. Validate exposure through kernel lineage and actual tc/skbmod usage rather than assuming all Linux deployments are practically affected.

Mitigation direction

  • Check whether vendor kernel updates include the referenced stable Linux fixes.
  • Prioritize updates on systems using CAN or other non-Ethernet interfaces.
  • Review traffic-control configurations for skbmod actions on non-Ethernet devices.
  • If patches are unavailable, follow Linux distribution vendor guidance.
  • Avoid deploying skbmod packet modification on non-Ethernet interfaces until fixed.

Validation and detection

  • Inventory Linux kernel versions against the affected version data.
  • Identify hosts using traffic control skbmod actions.
  • Check for non-Ethernet interfaces such as CAN on affected hosts.
  • Confirm installed kernels include the relevant stable commit fix.
  • Run safe packet-integrity regression tests for affected traffic paths.
Prepared
Confidence
medium
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2021-47293 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
2ADP providers
6Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux86da71b57383d40993cb90baafb3735cffe5d800, 86da71b57383d40993cb90baafb3735cffe5d800, 86da71b57383d40993cb90baafb3735cffe5d800, 86da71b57383d40993cb90baafb3735cffe5d800, 86da71b57383d40993cb90baafb3735cffe5d800unaffected
LinuxLinux4.9, 0, 4.19.199, 5.4.136, 5.10.54, 5.13.6, 5.14affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.