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CVE Record

CVE-2026-31717: ksmbd: validate owner of durable handle on reconnect

In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate owner of durable handle on reconnect Currently, ksmbd does not verify if the user attempting to reconnect to a durable handle is the same user who originally opened the file. This allows any authenticated user to hijack an orphaned durable handle by predicting or brute-forcing the persistent ID. According to MS-SMB2, the server MUST verify that the SecurityContext of the reconnect request matches the SecurityContext associated with the existing open. Add a durable_owner structure to ksmbd_file to store the original opener's UID, GID, and account name. and catpure the owner information when a file handle becomes orphaned. and implementing ksmbd_vfs_compare_durable_owner() to validate the identity of the requester during SMB2_CREATE (DHnC).

HighCVSS 8.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A flaw in Linux ksmbd can let an authenticated SMB user take over another user's disconnected durable file handle. If successful, the attacker could access or alter files through that handle and disrupt service. The issue is remotely reachable where affected ksmbd file sharing is enabled.

Executive priority

Prioritize affected, network-reachable ksmbd servers, especially those serving sensitive or shared data. The 8.8 CVSS rating reflects possible high confidentiality, integrity, and availability impact, although authentication is required and active exploitation is not documented.

Technical view

During SMB2 durable-handle reconnection, ksmbd failed to confirm that the requester matched the original handle owner. An authenticated user could predict or brute-force an orphaned handle's persistent ID. The referenced fixes retain the opener's UID, GID, and account name, then compare that identity during reconnect.

Likely exposure

Exposure is limited to systems running affected Linux kernel versions with ksmbd enabled and reachable by authenticated SMB users. The bundle marks 6.9, 6.6.142, 6.12.92, 6.18.25, 7.0.2, and 7.1 as affected, but provides no CPEs; confirm distribution-specific package status.

Exploitation context

No active exploitation is established: KEV is false, and the supplied sources report no observed attacks. Exploitation requires SMB authentication, an orphaned durable handle, and discovery of its persistent ID. Internet-facing or broadly accessible SMB services have greater practical exposure.

Researcher notes

The issue concerns SMB2_CREATE durable-handle reconnect processing, identified as DHnC in the description. Owner state must survive orphaning and be validated on reconnect. No CWE or CPE is supplied. Version entries mix release numbers and commit identifiers, so downstream vendor advisories are needed for precise package mapping.

Mitigation direction

  • Inventory systems using ksmbd and compare their kernel packages with vendor advisories.
  • Apply vendor kernel updates containing the referenced durable-owner validation fix.
  • Restrict SMB access to trusted users and networks while updates are pending.
  • Review vendor guidance before applying compensating controls not documented in the supplied sources.

Validation and detection

  • Confirm ksmbd is enabled and determine which interfaces can reach the SMB service.
  • Record the running kernel and distribution package version on each ksmbd host.
  • Verify the installed package includes the referenced stable fix or vendor backport.
  • After updating, confirm durable reconnects reject requests from a different authenticated identity.
Prepared
Confidence
medium
Sources
7

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

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CVE-2026-31717 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
6Source 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-2026-31717Attack 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
LinuxLinux8df4bcdb0a4232192b2445256c39b787d58ef14d, c8efcc786146a951091588e5fa7e3c754850cb3c, c8efcc786146a951091588e5fa7e3c754850cb3c, c8efcc786146a951091588e5fa7e3c754850cb3c, c8efcc786146a951091588e5fa7e3c754850cb3c, 6.6.32unaffected
LinuxLinux6.9, 0, 6.6.142, 6.12.92, 6.18.25, 7.0.2, 7.1affected
Weakness

CWE details

No CWE listed

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