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CVE Record

CVE-2021-46923: fs/mount_setattr: always cleanup mount_kattr

In the Linux kernel, the following vulnerability has been resolved: fs/mount_setattr: always cleanup mount_kattr Make sure that finish_mount_kattr() is called after mount_kattr was succesfully built in both the success and failure case to prevent leaking any references we took when we built it. We returned early if path lookup failed thereby risking to leak an additional reference we took when building mount_kattr when an idmapped mount was requested.

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 resource cleanup flaw. When an idmapped mount request was built successfully but later path lookup failed, the kernel could return early without releasing references. The source does not provide CVSS, a confirmed impact beyond reference leakage, or evidence of active exploitation.

Executive priority

Handle through standard kernel maintenance unless vendor guidance raises severity. The available evidence supports patch tracking, not emergency response, because exploit status and business impact are not established in the provided sources.

Technical view

The bug is in fs/mount_setattr cleanup handling. finish_mount_kattr() was not always called after mount_kattr was built, creating a reference leak on an error path involving idmapped mounts and failed path lookup. Kernel stable commits are referenced as fixes, but the bundle does not name package versions carrying them.

Likely exposure

Exposure is limited to Linux systems running affected kernel builds identified in the CVE bundle, including 5.12, 5.15.13, and 5.16. Systems without the referenced stable fixes should be treated as potentially affected.

Exploitation context

The bundle marks KEV as false and provides no cited evidence of active exploitation. It also does not provide exploitability requirements, attacker privileges, or practical impact beyond leaked references in the kernel error path.

Researcher notes

Key uncertainty is impact. The record describes a reference leak but does not map it to denial of service, privilege escalation, or containment escape. Validate affectedness by source or vendor backport status rather than upstream version numbers alone.

Mitigation direction

  • Check Linux vendor advisories for fixed kernel packages.
  • Upgrade to a kernel containing the referenced stable fixes.
  • Prioritize systems running affected kernel versions from the bundle.
  • Track remediation through normal kernel patch management.
  • Reboot systems if required by the kernel update process.

Validation and detection

  • Inventory Linux kernel versions across managed assets.
  • Confirm whether the referenced stable commits are present.
  • Compare vendor kernel packages against vendor CVE guidance.
  • Verify patched systems boot into the updated kernel.
  • Document any systems awaiting vendor backports.
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

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-2021-46923 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

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux9caccd41541a6f7d6279928d9f971f6642c361af, 9caccd41541a6f7d6279928d9f971f6642c361afunaffected
LinuxLinux5.12, 0, 5.15.13, 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.