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CVE Record

CVE-2025-38321: smb: Log an error when close_all_cached_dirs fails

In the Linux kernel, the following vulnerability has been resolved: smb: Log an error when close_all_cached_dirs fails Under low-memory conditions, close_all_cached_dirs() can't move the dentries to a separate list to dput() them once the locks are dropped. This will result in a "Dentry still in use" error, so add an error message that makes it clear this is what happened: [ 495.281119] CIFS: VFS: \\otters.example.com\share Out of memory while dropping dentries [ 495.281595] ------------[ cut here ]------------ [ 495.281887] BUG: Dentry ffff888115531138{i=78,n=/} still in use (2) [unmount of cifs cifs] [ 495.282391] WARNING: CPU: 1 PID: 2329 at fs/dcache.c:1536 umount_check+0xc8/0xf0 Also, bail out of looping through all tcons as soon as a single allocation fails, since we're already in trouble, and kmalloc() attempts for subseqeuent tcons are likely to fail just like the first one did.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Under low-memory conditions, Linux’s SMB/CIFS client may fail to release cached directory entries while closing connections or unmounting a share, producing a kernel warning that entries remain in use. The supplied CVSS rates potential confidentiality, integrity, and availability impacts as high, but the source narrative only demonstrates the cleanup failure and warning.

Executive priority

Schedule expedited remediation for affected SMB client systems, especially multi-user servers or systems prone to memory pressure. CVSS 7.8 supports high priority, but the absence of KEV evidence and incomplete explanation of security impact do not support treating this as a confirmed active-exploitation emergency.

Technical view

An allocation failure in close_all_cached_dirs() can prevent dentries from being moved to a temporary list for dput() after locks are released. This leaves dentries referenced during CIFS unmount checks. The referenced resolution adds an explicit out-of-memory error and stops processing additional tree connections after the first allocation failure.

Likely exposure

Candidates are Linux systems running versions explicitly marked affected—6.13, 0, 6.6.95, 6.12.35, 6.15.4, and 6.16—that use SMB/CIFS client functionality. The version data is unusual and mixes affected and unaffected stable releases, so administrators should verify distribution backports rather than relying only on version strings.

Exploitation context

The bundle reports no KEV listing or evidence of active exploitation. The supplied vector describes local, low-complexity exploitation requiring low privileges and no user interaction. The technical narrative additionally requires memory pressure during SMB cached-directory cleanup, but does not establish reliable exploitation, remote triggering, or the claimed complete confidentiality, integrity, and availability impacts.

Researcher notes

The record is unusual: the described resolution primarily improves diagnostic logging and stops further allocation attempts, while the supplied CVSS asserts complete confidentiality, integrity, and availability impacts. The bundle does not explain that impact path. Validate CNA version metadata, patch semantics, and distribution backports before making exploitability claims.

Mitigation direction

  • Apply a vendor-supported kernel containing the referenced stable fix or an equivalent distribution backport.
  • Confirm the exact remediated build through Linux distribution or appliance-vendor guidance.
  • Prioritize affected systems that actively mount SMB/CIFS shares and face memory-pressure risk.
  • Maintain memory headroom on affected SMB clients until the appropriate kernel update is installed.

Validation and detection

  • Inventory kernel versions on systems using SMB/CIFS client mounts.
  • Check distribution package metadata for backports of the referenced upstream commits.
  • Review kernel logs for CIFS out-of-memory and “Dentry still in use” messages.
  • After updating, confirm systems booted into the remediated kernel build.
Prepared
Confidence
medium
Sources
6

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.

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CVE-2025-38321 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
0ADP providers
5Source links

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:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2025-38321Attack 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.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux73934e535cffbda1490fa97d82690a0f9aa73e94, 548812afd96982a76a93ba76c0582ea670c40d9e, 3fa640d035e5ae526769615c35cb9ed4be6e3662, 3fa640d035e5ae526769615c35cb9ed4be6e3662, ff4528bbc82d0d90073751f7b49e7b9e9c7e5638, 6.6.64, 6.12.2, 6.11.11unaffected
LinuxLinux6.13, 0, 6.6.95, 6.12.35, 6.15.4, 6.16affected
Weakness

CWE details

No CWE listed

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