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Linux Kernel EUVDEUVD-2026-28695

| CVE-2026-43389 MEDIUM
2026-05-08 Linux GHSA-rmwg-23c2-w7hq
Information Disclosure Linux
5.5
CVSS 3.1 · NVD
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Severity by source

NVD PRIMARY
5.5 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
SUSE
MEDIUM
qualitative
Red Hat
MEDIUM
qualitative

Primary rating from NVD.

CVSS VectorNVD

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

5
Analysis Generated
Jun 08, 2026 - 11:34 vuln.today
CVSS changed
May 26, 2026 - 15:07 NVD
5.5 (MEDIUM)
Patch available
May 08, 2026 - 16:18 EUVD
CVE Published
May 08, 2026 - 14:21 nvd
MEDIUM 5.5
CVE Published
May 08, 2026 - 14:21 nvd
UNKNOWN (no severity yet)

DescriptionCVE.org

In the Linux kernel, the following vulnerability has been resolved:

mm: memfd_luo: always dirty all folios

A dirty folio is one which has been written to. A clean folio is its opposite. Since a clean folio has no user data, it can be freed under memory pressure.

memfd preservation with LUO saves the flag at preserve(). This is problematic. The folio might get dirtied later. Saving it at freeze() also doesn't work, since the dirty bit from PTE is normally synced at unmap and there might still be mappings of the file at freeze().

To see why this is a problem, say a folio is clean at preserve, but gets dirtied later. The serialized state of the folio will mark it as clean. After retrieve, the next kernel will see the folio as clean and might try to reclaim it under memory pressure. This will result in losing user data.

Mark all folios of the file as dirty, and always set the MEMFD_LUO_FOLIO_DIRTY flag. This comes with the side effect of making all clean folios un-reclaimable. This is a cost that has to be paid for participants of live update. It is not expected to be a common use case to preserve a lot of clean folios anyway.

Since the value of pfolio->flags is a constant now, drop the flags variable and set it directly.

AnalysisAI

The memfd_luo (memory file descriptor Live Update Operations) subsystem in the Linux kernel silently discards user data by incorrectly tracking folio dirty state across live kernel updates. Folios that are clean at preserve() time but subsequently written to are serialized as clean, causing the successor kernel to treat them as reclaimable under memory pressure - permanently destroying user data stored in those memory regions. This affects systems using the memfd LUO live kernel update feature, with fixes confirmed in Linux 6.19.9 and 7.0. No public exploit exists and EPSS is 0.02%, reflecting the niche deployment conditions required.

Technical ContextAI

This vulnerability resides in the Linux kernel's mm/memfd_luo subsystem, which implements memfd (memory file descriptor) preservation across Live Update Operations - a mechanism enabling in-place kernel upgrades without full system restart. The affected primitive is the folio dirty bit, which tracks whether a memory page contains user-written data versus kernel-initialized zero content. The root cause is a race between dirty-bit synchronization and the LUO state serialization lifecycle: the dirty flag from a page table entry (PTE) is normally synced back to the folio only at unmap time, but LUO's preserve() and freeze() checkpoints do not guarantee all PTEs have been unmapped and synced. Consequently, the serialized folio state may record a folio as clean even though live mappings will write to it before freeze completes. The fix marks all memfd LUO folios unconditionally dirty at preserve time, eliminating the race at the cost of preventing memory reclamation for all LUO participants. CPE data identifies the affected product as cpe:2.3:a:linux:linux:*:*:*:*:*:*:*:*. No CWE was assigned by NVD, but this aligns with CWE-362 (Race Condition) or CWE-672 (Operation on Resource After Expiration or Release) given the lifecycle ordering flaw.

RemediationAI

Upgrade to Linux kernel 6.19.9 or 7.0 (or later), which contain the upstream fix committing unconditional dirty-marking for all memfd LUO folios. The stable-branch patch is available at https://git.kernel.org/stable/c/e901c871d4b592f0042e30f3a0f031eae79744ec and the mainline patch at https://git.kernel.org/stable/c/7e04bf1f33151a30e06a65b74b5f2c19fc2be128. For enterprise Linux users on Red Hat or SUSE, apply vendor-issued kernel updates incorporating these commits once available through official channels. If immediate patching is not possible, a viable compensating control is to avoid performing live kernel updates (memfd LUO operations) on systems where data integrity of memfd-backed files is critical - this eliminates the attack surface entirely since the vulnerability only manifests during LUO preserve/freeze/retrieve cycles. Note that the upstream fix has a deliberate side effect: all LUO-participating folios become non-reclaimable under memory pressure, which may increase memory pressure on systems with large memfd workloads during live update operations. This trade-off is acceptable for correctness but should be accounted for in capacity planning.

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Vendor StatusVendor

SUSE

Severity: Medium
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise High Availability Extension 15 SP7 Fixed
SUSE Linux Enterprise High Availability Extension 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed

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EUVD-2026-28695 vulnerability details – vuln.today
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