Bug 2464401 (CVE-2026-31717)

Summary: CVE-2026-31717 kernel: ksmbd: validate owner of durable handle on reconnect
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
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Priority: unspecified    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in ksmbd, a component of the Linux kernel. This vulnerability allows an authenticated user to hijack an orphaned durable handle by predicting or brute-forcing its persistent ID. This could lead to unauthorized access to file sessions and potentially sensitive data or services.
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Description OSIDB Bzimport 2026-05-01 15:04:43 UTC 
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).
Comment 1 Keith Grant 2026-05-01 20:32:32 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026050124-CVE-2026-31717-f68b@gregkh/T