CVE-2026-89641: In the Linux kernel, the following vulnerability has been resolved: cifs: clear tcon after cifsFileInfo_put() in cifs_file_set

In the Linux kernel, the following vulnerability has been resolved: cifs: clear tcon after cifsFileInfo_put() in cifs_file_set_size() When the else branch of

In the Linux kernel, the following vulnerability has been resolved: cifs: clear tcon after cifsFileInfo_put() in cifs_file_set_size() When the else branch of cifs_file_set_size() finds a writable file handle via find_writable_file(), it borrows tcon and server from the handle's tlink, attempts the handle-based set_file_size() RPC, and then releases the handle with cifsFileInfo_put(). If set_file_size() fails, execution falls through to the path-based fallback, which reuses the borrowed tcon and server under the "if (tcon == NULL)" guard. Since tcon is not NULL at that point, the guard is skipped. If cifsFileInfo_put() dropped the last reference on a tlink that was already removed from the tlink tree (TCON_LINK_IN_TREE cleared, as happens during reconnection or session teardown), cifs_put_tlink() will have freed tcon; the subsequent set_path_size() call is then a use-after-free. Setting tcon = NULL after cifsFileInfo_put() causes the existing guard to take the cifs_sb_tlink() path, which acquires a fresh reference for the path-based operation or fails cleanly if the session is gone.

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 0.14%, higher than 3% of CVEs. That’s low, but low isn’t zero, and the odds jump the day someone publishes an exploit. Scored October 31, 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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