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

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-01 · updated 2026-06-17

Description

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).

Affected products

Linux kernel: from 6.6.32 before 6.7; from 6.9 before 6.18.25; from 6.19 before 7.0.2; 7.1-rc1 — fixed in 6.18.25, 6.7, 7.0.2

How to fix

Upgrade to a fixed version: Linux kernel 6.18.25, 6.7, 7.0.2. Check the vendor advisory for mitigations.

References

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