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CVE Record

CVE-2021-47116: ext4: fix memory leak in ext4_mb_init_backend on error path.

In the Linux kernel, the following vulnerability has been resolved: ext4: fix memory leak in ext4_mb_init_backend on error path. Fix a memory leak discovered by syzbot when a file system is corrupted with an illegally large s_log_groups_per_flex.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2021-47116 is a Linux kernel ext4 filesystem bug that can leak memory when handling a corrupted filesystem with an illegally large flex group setting. Business impact is most likely availability risk on systems that process malformed ext4 media or images. The provided sources do not include a CVSS score or evidence of active exploitation.

Executive priority

Handle through normal kernel patch management unless the organization processes untrusted filesystem images at scale. Escalate priority for forensic, hosting, sandboxing, build, or appliance environments where malformed ext4 content is routine.

Technical view

The issue is in ext4_mb_init_backend, where an error path failed to release allocated memory after encountering corrupted ext4 metadata, specifically an illegally large s_log_groups_per_flex. Kernel stable commits are referenced as fixes. The source bundle does not provide exploitability details, privilege requirements, or a CVSS vector.

Likely exposure

Exposure is most relevant to Linux systems using ext4 that may process corrupted or untrusted filesystems, disk images, or removable media. Systems that never mount or inspect untrusted ext4 content appear less exposed, based on the limited source evidence.

Exploitation context

The provided sources describe a syzbot-discovered memory leak caused by corrupted filesystem metadata. They do not show public exploitation, inclusion in CISA KEV, weaponized proof-of-concept activity, or remote attack conditions.

Researcher notes

The record identifies a memory leak in an ext4 error path, not memory corruption or privilege escalation. Evidence is sparse: no CVSS, CWE, detailed exploit preconditions, or impact rating are included. Analysis should stay tied to ext4 metadata handling and the referenced stable fixes.

Mitigation direction

  • Check distribution kernel advisories for CVE-2021-47116 coverage.
  • Apply vendor kernel updates containing the referenced ext4 stable fixes.
  • Avoid processing untrusted ext4 filesystems or disk images on sensitive hosts.
  • Use standard memory and availability monitoring on exposed Linux systems.

Validation and detection

  • Inventory Linux kernel versions on ext4-capable systems.
  • Confirm vendor changelogs or packages include the referenced stable commits.
  • Identify workflows that mount or inspect external ext4 media or images.
  • Review logs for kernel memory pressure or ext4 errors around untrusted media handling.
Prepared
Confidence
medium
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-2021-47116 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
4Source 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
LinuxLinuxdf61d3cff422433527d3bc388f69484f0781d226, f91436d55a279f045987e8b8c1385585dca54be9, f91436d55a279f045987e8b8c1385585dca54be9, 9e7af67e9521fb5cbb5b01aca22921c313c2e48eunaffected
LinuxLinux5.12, 0, 5.10.43, 5.12.10, 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.