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CVE Record

CVE-2025-37777: ksmbd: fix use-after-free in __smb2_lease_break_noti()

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in __smb2_lease_break_noti() Move tcp_transport free to ksmbd_conn_free. If ksmbd connection is referenced when ksmbd server thread terminates, It will not be freed, but conn->tcp_transport is freed. __smb2_lease_break_noti can be performed asynchronously when the connection is disconnected. __smb2_lease_break_noti calls ksmbd_conn_write, which can cause use-after-free when conn->ksmbd_transport is already freed.

HighCVSS 8.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A memory-safety flaw in the Linux kernel’s ksmbd SMB server can occur when an asynchronous lease notification uses transport memory already freed during disconnection. Successful exploitation could compromise confidentiality, integrity, and availability. Risk is concentrated on systems running affected kernels with ksmbd enabled and reachable.

Executive priority

Treat this as a high-priority infrastructure patch for exposed or sensitive ksmbd servers. Promptly establish whether ksmbd is actually enabled; systems using another SMB implementation are not established as affected by this record. Schedule normal accelerated remediation for isolated systems after vendor package validation.

Technical view

The connection object may remain referenced after the ksmbd server thread terminates, while its transport is freed. A later asynchronous __smb2_lease_break_noti() call can reach ksmbd_conn_write() through the stale transport, causing use-after-free. The kernel fix moves transport cleanup into ksmbd_conn_free(). CVSS 3.1 is 8.8: network-accessible, low complexity, low privileges, and no user interaction.

Likely exposure

Likely exposure is limited to Linux systems using the in-kernel ksmbd SMB server on affected kernel branches. Network reachability increases concern. The supplied affected-version data includes ambiguous entries and does not map fixes to distribution packages, so validate exposure against each Linux vendor’s advisory and kernel build.

Exploitation context

The supplied record does not establish active exploitation, and the CVE is not marked as present in CISA KEV. The CVSS vector indicates a network-adjacent attack path requiring low privileges, but the sources provide no verified public exploit status or observed attack campaign.

Researcher notes

The central race concerns differing lifetimes of the referenced connection and its transport during shutdown. Assessment should focus on asynchronous lease-break work after disconnect and whether the running branch contains the cleanup-lifetime change. The bundle provides four stable commits but insufficient branch mapping to declare exact fixed distribution versions.

Mitigation direction

  • Apply a vendor kernel release containing the referenced stable fix for your supported branch.
  • Prioritize reachable ksmbd servers and systems serving sensitive or business-critical data.
  • Until patched, restrict SMB access to trusted networks and authenticated users.
  • Disable ksmbd where SMB service is unnecessary, following vendor operational guidance.

Validation and detection

  • Inventory systems where ksmbd is enabled and identify broadly reachable SMB services.
  • Map running kernel packages to vendor advisories or the referenced stable fixes.
  • Confirm updated systems rebooted into the remediated kernel.
  • Review kernel logs for ksmbd faults around disconnect and lease-break activity.
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-2025-37777 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-2025-37777Attack 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, 6.6.101, 6.12.26, 6.14.4, 6.15affected
Weakness

CWE details

No CWE listed

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