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CVE Record

CVE-2021-47138: cxgb4: avoid accessing registers when clearing filters

In the Linux kernel, the following vulnerability has been resolved: cxgb4: avoid accessing registers when clearing filters Hardware register having the server TID base can contain invalid values when adapter is in bad state (for example, due to AER fatal error). Reading these invalid values in the register can lead to out-of-bound memory access. So, fix by using the saved server TID base when clearing filters.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel driver flaw in cxgb4. If the network adapter is already in a bad hardware state, the driver may read invalid register values and access memory outside expected bounds while clearing filters. Business urgency depends on whether affected kernels and this driver are present.

Executive priority

Treat as a targeted kernel maintenance item, not an emergency, unless critical servers use the affected driver and cannot be patched. The absence of CVSS, KEV, and exploit details lowers confidence in urgency, but kernel memory safety issues still merit scheduled remediation.

Technical view

The issue is in cxgb4 filter cleanup. When an adapter is in a bad state, such as after an AER fatal error, reading the server TID base from hardware registers can return invalid values, leading to out-of-bound memory access. The kernel fix uses the saved server TID base instead.

Likely exposure

Exposure appears limited to Linux systems running affected kernel versions with the cxgb4 driver in use. The bundle lists affected Linux versions and fixes around 5.4.124, 5.10.42, 5.12.9, and 5.13, but distro backports must be checked.

Exploitation context

No active exploitation is stated in the provided sources, and the CVE is not marked KEV. The trigger context involves a bad adapter state, including possible AER fatal error conditions. The bundle does not provide exploitability, attacker position, or privilege requirements.

Researcher notes

Key uncertainty is exploitability. The sources identify an out-of-bound memory access caused by invalid hardware register reads during filter clearing, but do not state impact beyond that condition. Validate exposure through driver usage, kernel branch, and vendor backport evidence.

Mitigation direction

  • Check vendor kernel advisories for fixed or backported cxgb4 patches.
  • Upgrade affected Linux kernels to a vendor-supported fixed build.
  • Prioritize systems using cxgb4-capable network adapters or loading the cxgb4 driver.
  • Monitor hosts for adapter fatal errors until patched.
  • Do not assume upstream version numbers reflect distro backport status.

Validation and detection

  • Inventory Linux kernel versions across affected server fleets.
  • Check whether the cxgb4 driver is present or loaded.
  • Map running kernels to vendor advisories for CVE-2021-47138.
  • Confirm fixed kernel packages are installed after maintenance.
  • Review kernel logs for adapter bad-state or AER fatal error events.
Prepared
Confidence
medium
Sources
6

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

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ATT&CK lookup starting points

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CVE-2021-47138 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
5Source 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
LinuxLinuxb1a79360ee862f8ada4798ad2346fa45bb41b527, b1a79360ee862f8ada4798ad2346fa45bb41b527, b1a79360ee862f8ada4798ad2346fa45bb41b527, b1a79360ee862f8ada4798ad2346fa45bb41b527unaffected
LinuxLinux5.2, 0, 5.4.124, 5.10.42, 5.12.9, 5.13affected
Weakness

CWE details

No CWE listed

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