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CVE Record

CVE-2021-46969: bus: mhi: core: Fix invalid error returning in mhi_queue

In the Linux kernel, the following vulnerability has been resolved: bus: mhi: core: Fix invalid error returning in mhi_queue mhi_queue returns an error when the doorbell is not accessible in the current state. This can happen when the device is in non M0 state, like M3, and needs to be waken-up prior ringing the DB. This case is managed earlier by triggering an asynchronous M3 exit via controller resume/suspend callbacks, that in turn will cause M0 transition and DB update. So, since it's not an error but just delaying of doorbell update, there is no reason to return an error. This also fixes a use after free error for skb case, indeed a caller queuing skb will try to free the skb if the queueing fails, but in that case queueing has been done.

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 MHI bus bug where queueing can report failure even after work was queued. Some callers may then free a network buffer that the kernel still uses, creating a use-after-free condition. The provided sources do not include a CVSS score, confirmed exploitation, or detailed business impact.

Executive priority

Handle through normal kernel patch management unless the environment relies on MHI-connected hardware at scale. Escalate priority for mobile, embedded, modem, or edge systems where affected kernels are deployed and patch status is unclear.

Technical view

The issue is in mhi_queue error handling when the MHI doorbell is inaccessible outside M0 state, such as M3. The fix treats delayed doorbell update as non-error because resume callbacks handle M3 exit. Returning an error after queueing could make skb callers free an already-queued buffer, causing use-after-free.

Likely exposure

Exposure appears limited to Linux systems running affected kernel versions or downstream builds with the vulnerable MHI core behavior, especially systems using MHI-connected hardware. The source bundle indicates Linux 5.12-era affected versions, but branch-specific backports must be verified with each vendor kernel.

Exploitation context

The supplied sources do not show active exploitation, and the source bundle marks KEV as false. No exploit prerequisites, attacker position, or public weaponization details are provided. Treat this as a kernel memory-safety issue with incomplete severity evidence.

Researcher notes

Evidence is thin: no CVSS, CWE, exploit report, or detailed affected-platform matrix is provided. The main confirmed behavior is invalid error propagation in mhi_queue leading to skb use-after-free. Validation should focus on kernel branch ancestry and vendor backport confirmation.

Mitigation direction

  • Apply Linux vendor kernel updates containing the referenced MHI core fixes.
  • Check distribution advisories for backported fixes in maintained kernel branches.
  • Prioritize systems using MHI-connected devices or modem hardware.
  • Avoid assuming fixed status from upstream version numbers alone.
  • Monitor kernel vendor guidance for severity and operational notes.

Validation and detection

  • Inventory kernel versions and vendor patch levels across Linux assets.
  • Identify systems with MHI bus support or MHI-connected hardware in use.
  • Confirm whether referenced stable commits or vendor backports are present.
  • Review crash logs for MHI or skb-related kernel instability.
  • Track whether distributions classify this CVE in their advisories.
Prepared
Confidence
medium
Sources
4

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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CVE-2021-46969 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
3Source 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
LinuxLinuxa8f75cb348fd52e7a5cf25991cdf9c89fb0cfd41, a8f75cb348fd52e7a5cf25991cdf9c89fb0cfd41unaffected
LinuxLinux5.12, 0, 5.12.3, 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.