Security readout for executives and security teams
Plain-English summary
CVE-2021-47342 is a Linux kernel ext4 bug that can leave a pointer to freed memory when an MMP-protected filesystem is remounted read-only. The public record does not provide CVSS, business impact, or confirmed exploit activity.
Executive priority
Treat this as a kernel maintenance item unless local evidence shows ext4 MMP use on critical systems. No source-provided severity score or exploitation evidence supports emergency handling.
Technical view
The issue is a possible use-after-free in ext4 MMP handling. After a prior ext4_fill_super change, the kmmpd thread could exit during read-only remount, leaving sbi->s_mmp_tsk pointing to freed memory before ext4_stop_mmpd() uses it. Stable kernel commits change kmmpd exit behavior.
Likely exposure
Exposure appears limited to Linux systems using ext4 filesystems with multiple-mount protection where affected kernel code is present. The bundle lists Linux kernel commit identifiers and version 5.10.51, but does not map distro packages or configurations.
Exploitation context
The provided sources do not show active exploitation, and the CVE is not listed as KEV. The record describes a race condition in kernel filesystem handling, not a remote attack path or public exploit.
Researcher notes
The core condition is a race between read-only remount and kmmpd lifecycle management, causing a stale task pointer. Impact details, exploitability constraints, and affected downstream package ranges are not provided in the bundle.
Mitigation direction
- Check vendor kernel advisories for CVE-2021-47342 coverage.
- Apply Linux kernel updates that include the referenced stable ext4 fixes.
- Prioritize systems using ext4 MMP on shared or sensitive storage.
- Avoid assuming fixed status from upstream version alone; verify distro backports.
Validation and detection
- Inventory Linux systems using ext4 with MMP enabled.
- Map deployed kernel packages to vendor fixes or referenced stable commits.
- Review operational workflows that remount ext4 filesystems read-only.
- Check kernel logs for ext4 or MMP related crashes or warnings.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
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-2021-47342 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
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.
SSVC decision data
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://git.kernel.org/stable/c/b663890d854403e566169f7e90aed5cd6ff64f6bCVE reference, Linux
- https://git.kernel.org/stable/c/7ed572cdf11081f8f9e07abd4bea56a3f2c4edbdCVE reference, Linux
- https://git.kernel.org/stable/c/61bb4a1c417e5b95d9edb4f887f131de32e419cbCVE reference, Linux
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.