CVE-2026-97564: In the Linux kernel, the following vulnerability has been resolved: smb: client: reject userspace cifs.idmap descriptions cifs.idmap key descriptions carry au

In the Linux kernel, the following vulnerability has been resolved: smb: client: reject userspace cifs.idmap descriptions cifs.idmap key descriptions carry au

In the Linux kernel, the following vulnerability has been resolved: smb: client: reject userspace cifs.idmap descriptions cifs.idmap key descriptions carry authority-bearing fields (owner and group SIDs and uid/gid values in "os:"/"gs:"/"oi:"/"gi:" form) that the cifs.idmap upcall helper treats as kernel-originating inputs. Unlike its sibling cifs.spnego, the cifs.idmap key type has no vet_description hook, so userspace can create keys of this type through request_key(2)/add_key(2) and supply those fields without CIFS origin. A request_key(2) call with a non-NULL callout then drives a root usermodehelper upcall (/sbin/request-key -> cifs.idmap) that consumes the unvetted description in root context. Only accept cifs.idmap descriptions while CIFS is using its private root_cred to request the key. id_to_sid()/sid_to_id() already run under override_creds(root_cred), so the kernel-originated path is unaffected. This mirrors commit 3da1fdf4efbc ("smb: client: reject userspace cifs.spnego descriptions"), which applied the same restriction to cifs.spnego.

Description from the National Vulnerability Database, published by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

What it means for a small business

Linux is on the computers, phones or browsers your team uses every day. Turn on automatic updates and restart: most of these fixes only take effect after a restart.

How likely is an attack? The Exploit Prediction Scoring System, run by FIRST (the global association of security response teams), puts the odds of this one being exploited in the next 30 days at 0.21%, higher than 11% of CVEs. That’s low, but low isn’t zero, and the odds jump the day someone publishes an exploit. Scored October 28, 2026, updated daily.

Check your own setup

Website check: reads what your site runs from the outside (WordPress version, plugins it can see, old server software) and matches it against this database.
Server check: what your web server says about itself, and whether that version has known flaws.

Sources

Part of the Huttenlocher Technologies vulnerability database, refreshed twice a day from CISA and the NVD. The title, category and plain-language guidance are ours; check the linked record before acting on a detail. This is general guidance, not a review of your systems.

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