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CVE Record

CVE-2025-21811: nilfs2: protect access to buffers with no active references

In the Linux kernel, the following vulnerability has been resolved: nilfs2: protect access to buffers with no active references nilfs_lookup_dirty_data_buffers(), which iterates through the buffers attached to dirty data folios/pages, accesses the attached buffers without locking the folios/pages. For data cache, nilfs_clear_folio_dirty() may be called asynchronously when the file system degenerates to read only, so nilfs_lookup_dirty_data_buffers() still has the potential to cause use after free issues when buffers lose the protection of their dirty state midway due to this asynchronous clearing and are unintentionally freed by try_to_free_buffers(). Eliminate this race issue by adjusting the lock section in this function.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2025-21811 is a Linux kernel nilfs2 filesystem flaw that can cause use-after-free memory corruption. Because the CVSS vector requires local, low-privilege access, this is mainly an escalation risk on systems where nilfs2 is available or reachable, not a remote internet-facing bug.

Executive priority

Patch on the normal high-severity kernel update path, with faster handling for multi-user servers, shared hosting, developer workstations, and container hosts. No provided evidence supports emergency treatment for internet-wide exploitation, but successful local exploitation could compromise the host.

Technical view

nilfs_lookup_dirty_data_buffers() accessed buffers attached to dirty folios/pages without holding the needed locks. Asynchronous dirty-state clearing during read-only degeneration could let buffers lose protection and be freed by try_to_free_buffers(), creating a race-driven use-after-free. Kernel stable commits adjust the lock section to remove the race.

Likely exposure

Linux systems running affected kernel versions and exposing nilfs2 functionality are the main concern. Exposure is lower where nilfs2 is absent, disabled, or unreachable by local users. Distribution backports may fix vulnerable-looking version numbers, so verify vendor package status, not only upstream version strings.

Exploitation context

The source bundle reports CVSS 7.8 with AV:L, PR:L, UI:N, and high confidentiality, integrity, and availability impact. CISA KEV status is false in the bundle, and no provided source states active exploitation. Treat this as a local privilege and stability risk.

Researcher notes

The evidence identifies a nilfs2 race around dirty data buffers and folio/page locking. The affected-version data in the bundle is noisy, including repeated commit-like entries, so rely on upstream commits and distribution advisories for exact fixed package mapping.

Mitigation direction

  • Apply Linux kernel updates from your distribution or vendor.
  • Prioritize systems allowing local user access or untrusted workloads.
  • Verify vendor kernels include the linked upstream stable fixes or backports.
  • Disable or restrict nilfs2 where it is not operationally required.
  • Track Debian LTS advisories if running affected Debian releases.

Validation and detection

  • Inventory kernel packages and compare against vendor CVE advisories.
  • Check whether nilfs2 is built, loadable, or operationally used.
  • Confirm patched kernels include the relevant stable commit or vendor backport.
  • Review local-user and workload boundaries on exposed Linux hosts.
  • Retest after rebooting into the updated kernel.
Prepared
Confidence
medium
Sources
12

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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cwe · low confidence lookup

CWE-416: Exact CWE lookup

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cve · low confidence lookup

CVE-2025-21811 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

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

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
11Source links

SSVC decision data

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

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
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2025-21811Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

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
LinuxLinux8c26c4e2694a163d525976e804d81cd955bbb40c, 8c26c4e2694a163d525976e804d81cd955bbb40c, 8c26c4e2694a163d525976e804d81cd955bbb40c, 8c26c4e2694a163d525976e804d81cd955bbb40c, 8c26c4e2694a163d525976e804d81cd955bbb40c, 8c26c4e2694a163d525976e804d81cd955bbb40c, 8c26c4e2694a163d525976e804d81cd955bbb40c, 8c26c4e2694a163d525976e804d81cd955bbb40cunaffected
LinuxLinux3.10, 0, 5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.76, 6.12.13, 6.13.2, 6.14affected
Weakness

CWE details

CWE-416

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-416 · source CWE mapping

Use After Free

Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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