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CVE Record

CVE-2021-47520: can: pch_can: pch_can_rx_normal: fix use after free

In the Linux kernel, the following vulnerability has been resolved: can: pch_can: pch_can_rx_normal: fix use after free After calling netif_receive_skb(skb), dereferencing skb is unsafe. Especially, the can_frame cf which aliases skb memory is dereferenced just after the call netif_receive_skb(skb). Reordering the lines solves the issue.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2021-47520 is a Linux kernel bug in the pch_can CAN driver. The driver could use packet memory after handing it to the network stack, creating a use-after-free condition. The public record does not provide CVSS, impact details, or active exploitation evidence.

Executive priority

Handle through normal kernel patch management, with higher priority for operational technology, embedded, or vehicle-adjacent systems using CAN interfaces. There is not enough public evidence to justify emergency response solely from this CVE record.

Technical view

In pch_can_rx_normal, code dereferenced skb-backed can_frame data after netif_receive_skb(skb). The CVE states that dereferencing skb after that call is unsafe and that reordering the operations resolves the issue. Upstream stable kernel commits are referenced as fixes.

Likely exposure

Exposure appears limited to Linux systems running affected kernel versions with the pch_can CAN driver present and used. The CVE data has no CPEs and only lists Linux kernel versions and commits, so environment-specific validation is required.

Exploitation context

The source bundle does not report public exploitation, KEV listing, exploitability conditions, privilege requirements, or attacker position. Treat this as a kernel memory-safety issue until vendor advisories or distribution notices clarify impact.

Researcher notes

The key issue is lifetime ordering around skb ownership transfer to netif_receive_skb. The record says reordering fixes the unsafe dereference, but does not document practical impact, reachability, crashability, or privilege boundaries.

Mitigation direction

  • Update to a kernel containing the referenced upstream stable pch_can fix.
  • Check Linux distribution advisories for backported fixes and package names.
  • Prioritize systems that use CAN interfaces or load the pch_can driver.
  • If immediate patching is not possible, review vendor guidance for safe temporary mitigations.

Validation and detection

  • Inventory Linux kernel versions against the CVE affected-version data.
  • Check whether the pch_can driver is built, installed, or loaded.
  • Confirm updated kernels include one of the referenced stable commits or a vendor backport.
  • Review vendor security advisories for corrected package versions.
Prepared
Confidence
medium
Sources
10

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-2021-47520 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
9Source 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
LinuxLinuxb21d18b51b31a24d17f883b678432fbdee3d5675, b21d18b51b31a24d17f883b678432fbdee3d5675, b21d18b51b31a24d17f883b678432fbdee3d5675, b21d18b51b31a24d17f883b678432fbdee3d5675, b21d18b51b31a24d17f883b678432fbdee3d5675, b21d18b51b31a24d17f883b678432fbdee3d5675, b21d18b51b31a24d17f883b678432fbdee3d5675, b21d18b51b31a24d17f883b678432fbdee3d5675unaffected
LinuxLinux2.6.37, 0, 4.4.295, 4.9.293, 4.14.258, 4.19.221, 5.4.165, 5.10.85, 5.15.8, 5.16affected
Weakness

CWE details

No CWE listed

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