CVE-2026-64294 Affecting kernel-default-livepatch package, versions <6.4.0-150700.53.81.1


Severity

Recommended
0.0
medium
0
10

Based on SUSE Linux Enterprise Server security rating.

Threat Intelligence

EPSS
0.16% (6th percentile)

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  • Snyk IDSNYK-SLES157-KERNELDEFAULTLIVEPATCH-19909684
  • published18 Sept 2026
  • disclosed17 Sept 2026

Introduced: 17 Sep 2026

NewCVE-2026-64294  (opens in a new tab)

How to fix?

Upgrade SLES:15.7 kernel-default-livepatch to version 6.4.0-150700.53.81.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-default-livepatch package and not the kernel-default-livepatch package as distributed by SLES. See How to fix? for SLES:15.7 relevant fixed versions and status.

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

mm: do file ownership checks with the proper mount idmap

Ever since idmapped mounts were introduced, inode ownership checks (for side-channel protection) in mincore() and madvise(MADV_PAGEOUT) were done against the nop_mnt_idmap, which completely ignores the file's mount's idmap. This results in odd edgecases like:

  1. mount/bind-mount with an idmap userA:userB:1
  2. userB runs an owner_or_capable() check on file that is owned by userA on-disk/in-memory, but owned by userB after idmap translation
  3. owner_or_capable() mysteriously fails as the correct idmap wasn't supplied

In the case of mincore/madvise MADV_PAGEOUT, this is usually benign, because file_permission(file, MAY_WRITE) will probably succeed, as it uses the proper idmap internally, but it does not need to be the case on e.g a 0444 file where even the owner itself doesn't have permissions to write to it.

Since this is clearly not trivial to get right, introduce a file_owner_or_capable() that can carry the correct semantics, and switch the various users in mm to it.

The issue was found by manual code inspection & an off-list discussion with Jan Kara.

CVSS Base Scores

version 3.1