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CVE Record

CVE-2021-47170: USB: usbfs: Don't WARN about excessively large memory allocations

In the Linux kernel, the following vulnerability has been resolved: USB: usbfs: Don't WARN about excessively large memory allocations Syzbot found that the kernel generates a WARNing if the user tries to submit a bulk transfer through usbfs with a buffer that is way too large. This isn't a bug in the kernel; it's merely an invalid request from the user and the usbfs code does handle it correctly. In theory the same thing can happen with async transfers, or with the packet descriptor table for isochronous transfers. To prevent the MM subsystem from complaining about these bad allocation requests, add the __GFP_NOWARN flag to the kmalloc calls for these buffers.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysislow

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue is about an overly large USB filesystem transfer request causing a kernel warning, not confirmed memory corruption or compromise. The source says the request is invalid and handled correctly. Business urgency appears low, but exact severity is not published.

Executive priority

Treat as routine kernel hygiene unless your environment gives untrusted users local USB or usbfs access. There is no cited evidence of exploitation, privilege escalation, or data exposure in the supplied sources.

Technical view

usbfs bulk, async, or isochronous allocation paths could request excessively large buffers and trigger MM subsystem WARN messages. The kernel change adds __GFP_NOWARN to relevant kmalloc calls so invalid user requests do not generate warnings.

Likely exposure

Exposure is limited to Linux systems running affected kernel versions with user access to usbfs USB transfer interfaces. The bundle lists affected Linux versions/ranges including 3.3, 4.19.193, 5.4.124, 5.10.42, 5.12.9, and 5.13.

Exploitation context

No active exploitation is cited, and the CVE is not listed as KEV in the provided bundle. The source describes syzbot finding a warning condition from an invalid request, with usbfs handling it correctly.

Researcher notes

The issue appears to be warning suppression for invalid usbfs allocation requests, not a demonstrated memory safety flaw. Source detail is sparse: no CVSS, CWE, exploitability analysis, or distribution-specific fix matrix is provided.

Mitigation direction

  • Check your distribution kernel advisory for CVE-2021-47170 status.
  • Upgrade to a kernel containing the referenced stable fixes.
  • Prioritize internet-facing appliance fleets only if they expose local USB/user access paths.
  • Track vendor guidance before applying custom kernel changes.

Validation and detection

  • Inventory Linux kernel versions across servers, endpoints, and appliances.
  • Confirm whether usbfs access is available to untrusted local users.
  • Verify the running kernel includes the relevant stable commit or vendor backport.
  • Review kernel logs for recurring usbfs allocation warning patterns.
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-2021-47170 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

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxadd1aaeabe6b08ed26381a2a06e505b2f09c3ba5, add1aaeabe6b08ed26381a2a06e505b2f09c3ba5, add1aaeabe6b08ed26381a2a06e505b2f09c3ba5, add1aaeabe6b08ed26381a2a06e505b2f09c3ba5, add1aaeabe6b08ed26381a2a06e505b2f09c3ba5unaffected
LinuxLinux3.3, 0, 4.19.193, 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.