CVE-2025-21907: In the Linux kernel, the following vulnerability has been resolved: mm: memory-failure: update ttu flag inside unmap_poisoned_folio Patch series "mm: memory

In the Linux kernel, the following vulnerability has been resolved: mm: memory-failure: update ttu flag inside unmap_poisoned_folio Patch series "mm: memory_f

In the Linux kernel, the following vulnerability has been resolved: mm: memory-failure: update ttu flag inside unmap_poisoned_folio Patch series "mm: memory_failure: unmap poisoned folio during migrate properly", v3. Fix two bugs during folio migration if the folio is poisoned. This patch (of 3): Commit 6da6b1d4a7df ("mm/hwpoison: convert TTU_IGNORE_HWPOISON to TTU_HWPOISON") introduce TTU_HWPOISON to replace TTU_IGNORE_HWPOISON in order to stop send SIGBUS signal when accessing an error page after a memory error on a clean folio. However during page migration, anon folio must be set with TTU_HWPOISON during unmap_*(). For pagecache we need some policy just like the one in hwpoison_user_mappings to set this flag. So move this policy from hwpoison_user_mappings to unmap_poisoned_folio to handle this warning properly. Warning will be produced during unamp poison folio with the following log: ------------[ cut here ]------------ WARNING: CPU: 1 PID: 365 at mm/rmap.c:1847 try_to_unmap_one+0x8fc/0xd3c Modules linked in: CPU: 1 UID: 0 PID: 365 Comm: bash Tainted: G W 6.13.0-rc1-00018-gacdb4bbda7ab #42 Tainted: [W]=WARN Hardware name: QEMU QEMU Virtu

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 0.20%, higher than 10% 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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