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CVE Record

CVE-2021-46920: dmaengine: idxd: Fix clobbering of SWERR overflow bit on writeback

In the Linux kernel, the following vulnerability has been resolved: dmaengine: idxd: Fix clobbering of SWERR overflow bit on writeback Current code blindly writes over the SWERR and the OVERFLOW bits. Write back the bits actually read instead so the driver avoids clobbering the OVERFLOW bit that comes after the register is read.

MediumCVSS 5.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-46920 is a Linux kernel flaw in the idxd DMA engine driver. A local low-privilege user could affect integrity by triggering incorrect error-bit handling. The provided sources do not indicate remote exploitation or active exploitation. Prioritize Linux hosts where the idxd driver or Intel DSA-related functionality is present.

Executive priority

Treat as a moderate Linux platform hygiene issue. It is local-only and not KEV-listed, but integrity impact is high in the CVSS vector. Patch through normal kernel maintenance, with faster handling for shared systems or hosts exposing relevant accelerator hardware.

Technical view

The idxd dmaengine driver blindly wrote back SWERR and OVERFLOW bits, potentially clobbering OVERFLOW after the register was read. The kernel fix writes back only the bits actually read. CVSS v3.1 is 5.5: local attack vector, low complexity, low privileges, no user interaction, unchanged scope, high integrity impact.

Likely exposure

Exposure is limited to affected Linux kernel versions or commit ranges identified by the CVE data. Practical risk is most relevant where the idxd driver is built, loaded, or hardware-supported. Distro package status is not provided in the bundle and must be checked separately.

Exploitation context

The CVSS vector requires local access with low privileges. The source bundle marks KEV as false and provides no evidence of exploitation in the wild. No exploit details are included in the cited sources.

Researcher notes

Evidence is limited to the CVE record and Linux stable commit references. The vulnerability is a driver state-handling defect around SWERR and OVERFLOW writeback. Do not assume distro impact or exploitability without confirming kernel configuration, loaded modules, hardware presence, and vendor package backports.

Mitigation direction

  • Apply vendor-supported Linux kernel updates containing the referenced stable fixes.
  • Check your Linux distribution advisory for CVE-2021-46920 package status.
  • Prioritize systems with idxd or DMA engine functionality enabled.
  • Limit unnecessary local user access on affected systems.
  • Track kernel versions against the CVE affected ranges before closure.

Validation and detection

  • Inventory Linux kernel versions across servers and images.
  • Check whether the idxd driver is present, built, or loaded.
  • Map installed kernels to vendor advisories for CVE-2021-46920.
  • Confirm patched kernels include the referenced stable commits.
  • Document exceptions where affected hardware or driver paths are absent.
Prepared
Confidence
high
Sources
5

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-2021-46920 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
5.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

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.

1CVSS vectors
3Timeline events
2ADP providers
4Source links

SSVC decision data

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

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
5.5CVSS 3.1MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N1.83.6CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

5.5Medium
CVSS 3.1 vector shape for CVE-2021-46920Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

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
cvssV3_1other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxbfe1d56091c1a404b3d4ce7e9809d745fc4453bb, bfe1d56091c1a404b3d4ce7e9809d745fc4453bb, bfe1d56091c1a404b3d4ce7e9809d745fc4453bbunaffected
LinuxLinux5.6, 0, 5.10.32, 5.11.16, 5.12affected
Weakness

CWE details

No CWE listed

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