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CVE Record

CVE-2025-37776: ksmbd: fix use-after-free in smb_break_all_levII_oplock()

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in smb_break_all_levII_oplock() There is a room in smb_break_all_levII_oplock that can cause racy issues when unlocking in the middle of the loop. This patch use read lock to protect whole loop.

HighCVSS 8.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A race condition in Linux kernel SMB server code can trigger use-after-free memory access. The supplied CVSS assessment rates potential confidentiality, integrity, and availability impact as high. Risk is concentrated on systems running the affected kernel code with ksmbd enabled and reachable.

Executive priority

Prioritize internet-facing or broadly reachable ksmbd servers and systems serving less-trusted users. Treat remediation as high priority, while validating actual ksmbd use before escalating fleet-wide emergency action. There is no supplied evidence of active exploitation.

Technical view

smb_break_all_levII_oplock() could unlock while iterating, allowing concurrent activity to invalidate referenced memory. The kernel fix protects the entire loop with a read lock. CVSS 3.1 is 8.8: network-reachable, low complexity, low privileges required, no user interaction, and high potential impact.

Likely exposure

Potentially exposed assets are Linux systems using ksmbd on affected kernels, particularly where SMB is network-accessible to low-privileged authenticated users. The bundle names versions or branches including 5.15, 6.6.88, 6.12.25, 6.14.4, and 6.15, but does not provide complete range semantics.

Exploitation context

The supplied record does not list this CVE in KEV and provides no evidence of active exploitation or public weaponization. The CVSS vector indicates network access and low privileges are required. Practical exploitability and reliable outcomes are not established by the supplied sources.

Researcher notes

The source description identifies a race-created use-after-free and a locking correction, but does not document a reproducer, crash signature, affected range boundaries, or demonstrated exploitation primitive. Review the stable commits and vendor backports when determining exposure; kernel version strings alone may be insufficient.

Mitigation direction

  • Identify systems running ksmbd and determine whether SMB is reachable from untrusted networks.
  • Update to a vendor-supported kernel containing the applicable referenced stable fix.
  • If immediate updating is impossible, disable ksmbd where it is not operationally required.
  • Restrict SMB access to trusted users and networks while remediation is pending.
  • Check distribution or appliance vendor guidance for exact fixed package versions.

Validation and detection

  • Record each system's kernel and vendor package version.
  • Confirm whether the ksmbd service or module is enabled and actively serving SMB.
  • Compare installed packages against vendor advisories and the referenced stable commits.
  • Verify network controls prevent unintended SMB access.
  • After updating, confirm the running kernel includes the applicable fix.
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.

ATT&CK lookup starting points

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CVE-2025-37776 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/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
8.8CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H2.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

8.8High
CVSS 3.1 vector shape for CVE-2025-37776Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/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
LinuxLinux0626e6641f6b467447c81dd7678a69c66f7746cf, 0626e6641f6b467447c81dd7678a69c66f7746cf, 0626e6641f6b467447c81dd7678a69c66f7746cf, 0626e6641f6b467447c81dd7678a69c66f7746cfunaffected
LinuxLinux5.15, 0, 6.6.88, 6.12.25, 6.14.4, 6.15affected
Weakness

CWE details

No CWE listed

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