CVE-2026-64027: In the Linux kernel, the following vulnerability has been resolved: net: shaper: rework the VALID marking (again) Recent commit changed the semantics from NOT

In the Linux kernel, the following vulnerability has been resolved: net: shaper: rework the VALID marking (again) Recent commit changed the semantics from NOT

In the Linux kernel, the following vulnerability has been resolved: net: shaper: rework the VALID marking (again) Recent commit changed the semantics from NOT_VALID to VALID. I didn't realize that the flags are not stored atomically with the entry in XArray. There's still a race of reader observing a VALID mark for a slot, getting interrupted, writer replacing the entry with a different one, reader continuing, fetching the entry which is now a different pointer than the pointer for which VALID was meant. The biggest consequence of this is that we may see a UAF since net_shaper_rollback() assumed that entries without VALID can be freed without observing RCU. Looks like the XArray marks are buying us nothing at this point. Let's convert the code to an explicit valid field. The smp_load_acquire() / smp_store_release() barriers are marginally cleaner.

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 under 0.1%, higher than 0% of CVEs. That’s low, but low isn’t zero, and the odds jump the day someone publishes an exploit. Scored October 29, 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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