CVE-2026-89760
High · 7.8CVSS
7.8
EPSS
0.2%
Published
Sep 11, 2026
CISA due date
—
Cloudanix analysis
A Linux kernel bug in hibernation handling can silently corrupt memory or crash programs when preparing to suspend the system.
- Exploitation
- Local Privilege
- Attacker needs
- Low Privilege
- Complexity
- Low
- Impact
- Full Compromise
- Component
- OS kernel
- Class
- Memory Corruption
- Remediation
- Patch
- Effort
- Medium
- Patch risk
- Low
What it actually does
The swap_free_hibernation_slot() function unconditionally frees a hibernation slot via __swap_cluster_free_entries() even when a folio remains in the swap cache (placed there by cluster readahead), violating the rule that such slots must only be freed when the cache reference drops. This leaves the folio unreachable from the swap table while its offset is returned to the allocator; later reclaim reuses the offset, causing folio->swap to reference a now-foreign entry and producing memory corruption.
Why it matters to the business
Linux systems performing hibernation (especially via uswsusp) may experience silent data corruption, application crashes, or unpredictable behavior across unrelated processes, potentially leading to data loss or unplanned downtime during suspend/resume cycles; low EPSS and absence from KEV indicate limited in-the-wild exploitation risk 43 days after disclosure.
How an attack unfolds
An attacker with local access triggers cluster readahead around a hibernation slot, causing a folio to be added to the swap cache; when swap_free_hibernation_slot() later runs during hibernation image preparation, it frees the slot prematurely, orphaning the folio; subsequent reclaim or allocation reuses the offset, corrupting memory for other userspace tasks.
How to fix it
Update the Linux kernel to a version containing the fix that adds a cached-folio check before calling __swap_cluster_free_entries() in swap_free_hibernation_slot(); rebuild and reboot with the corrected kernel; disable hibernation temporarily if immediate patching is not feasible.
How to confirm the fix worked
Verify the running kernel contains the commit that adds the __swap_cache_add_check() test before freeing hibernation slots; inspect /proc/version or kernel build logs for the patch; attempt hibernation on a test system with swap cache populated and confirm no corruption occurs.
Typical attack path
- Obtain local access on a Linux system using swap and hibernation
- Force swap activity that engages cluster readahead on a hibernation slot
- Initiate hibernation image creation (e.g., via uswsusp)
- Trigger premature slot free while folio resides in swap cache
- Allow reclaim to reuse the freed offset and corrupt unrelated memory
How to detect it
Search kernel logs and dmesg for swap or hibernation errors around uswsusp invocations; examine crash dumps for folio/swap table inconsistencies; review audit logs for unexpected local hibernation attempts.
What your security team should do
- Apply the upstream kernel patch at the earliest maintenance window given the memory-corruption severity
- Monitor EPSS and KEV status for any future rise in exploitability
- Restrict hibernation privileges to trusted users until patched
- Include kernel swap-subsystem changes in regular regression testing
The record
In the Linux kernel, the following vulnerability has been resolved: mm, swap: don't free a hibernation slot that is in the swap cache A slot with a folio in the swap cache is freed when the folio leaves the cache, not when its count drops. swap_put_entries_cluster() follows that rule. swap_free_hibernation_slot() does not, it calls __swap_cluster_free_entries() whether or not a folio sits on the slot. Cluster readahead can put one there. It walks a raw page_cluster sized window of offsets around the faulting entry, and a hibernation slot passes __swap_cache_add_check() because it is not a folio and its count is not zero. Freeing the slot then clears the entry under that folio. The folio is now unreachable from the swap table, and the offset goes back to the allocator. The folio is still on the LRU though, so reclaim can pick it up later. It then takes the old offset out of folio->swap and overwrites the table entry there, which by then may belong to someone else. This bug can trigger silent memory corruption, process crashes, or data instability across completely unrelated userspace applications - typically occurring when uswsusp is preparing the hibernation image. I found this while working on giving hibernation slots their own marker in the swap table, which I had discussed with Kairui. (https://lore.kernel.org/linux-mm/abp7aDgYLrxF3Me8@KASONG-MC4/) As far as I know there are no reports, so there is no Reported-by/Closes to add. Check for a cached folio before freeing. The slot is then left in the ordinary state where only the swap cache holds it, and it is freed when the folio leaves the cache, either through the reclaim below or through normal reclaim later.
Affected packages
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