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Linux Kernel EUVDEUVD-2026-39258

| CVE-2026-53167 MEDIUM
Use of Uninitialized Resource (CWE-908)
2026-06-25 416baaa9-dc9f-4396-8d5f-8c081fb06d67 GHSA-vg6g-9h68-878w
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
vuln.today AI
5.3 MEDIUM

AC:H reflects the non-default init_on_alloc=0 prerequisite; C:H captures kernel memory leakage explicitly described; A:L for potential aberrant FUSE behavior; AV:L and PR:L match CVSS and description constraints.

3.1 AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:L
4.0 AV:L/AC:H/AT:P/PR:L/UI:N/VC:H/VI:N/VA:L/SC:N/SI:N/SA:N
SUSE
MEDIUM
qualitative
Red Hat
7.0 MEDIUM
qualitative

Primary rating from NVD.

CVSS VectorNVD

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
Jul 06, 2026 - 20:27 vuln.today
CVSS changed
Jul 06, 2026 - 20:22 NVD
5.5 (MEDIUM)
Patch available
Jun 25, 2026 - 10:32 EUVD
CVE Published
Jun 25, 2026 - 09:16 nvd
MEDIUM 5.5
CVE Published
Jun 25, 2026 - 09:16 cve.org
UNKNOWN (no severity yet)

DescriptionNVD

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

fuse: limit FUSE_NOTIFY_RETRIEVE to uptodate folios

FUSE_NOTIFY_RETRIEVE must be limited to uptodate folios; !uptodate folios can contain uninitialized data. Since FUSE_NOTIFY_RETRIEVE is intended to only return data that is already in the page cache and not wait for data from the FUSE daemon, treat !uptodate folios as if they weren't present.

This only has security impact on systems that don't enable automatic zero-initialization of all page allocations via CONFIG_INIT_ON_ALLOC_DEFAULT_ON or init_on_alloc=1.

AnalysisAI

Uninitialized memory exposure in the Linux kernel FUSE subsystem allows a local attacker to read residual kernel page cache data via the FUSE_NOTIFY_RETRIEVE notification path. The flaw affects systems where folios not marked 'uptodate' are returned to FUSE daemons rather than treated as absent - a condition with direct security impact only on kernels built or booted without automatic page-allocation zeroing (CONFIG_INIT_ON_ALLOC_DEFAULT_ON or init_on_alloc=1). No public exploit has been identified at time of analysis and EPSS sits at 0.17% (6th percentile), reflecting minimal observed exploitation activity.

Technical ContextAI

The Linux kernel FUSE (Filesystem in Userspace) subsystem implements a FUSE_NOTIFY_RETRIEVE mechanism allowing FUSE daemons to request data already cached in the kernel page cache. CWE-908 (Use of Uninitialized Resource) manifests here because the kernel could return folios - the modern kernel page cache unit - that are not in the 'uptodate' state, meaning their contents have not been populated with valid data from a backing store and may contain residual bytes from prior allocations. The affected code path spans kernel versions from commit 2d45ba381a74a743eeaa2b06c7c5c0d2bf73ba1a onward. CPE cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* covers the full breadth. The kernel's CONFIG_INIT_ON_ALLOC_DEFAULT_ON option (or runtime init_on_alloc=1) zero-fills pages on allocation, which eliminates the uninitialized-data exposure but is not enabled by default in all distributions.

RemediationAI

Upgrade to Linux kernel 7.1, 7.0.13, or 6.18.36, which contain the targeted fix treating non-uptodate folios as absent in FUSE_NOTIFY_RETRIEVE. Patch commits are tracked in the kernel stable tree at https://git.kernel.org/stable/c/. As a compensating control on systems that cannot be patched immediately, enabling kernel page allocation zeroing via the boot parameter init_on_alloc=1 (or building with CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y) eliminates the uninitialized memory exposure, though it carries a measurable performance overhead - typically 1-5% on memory-intensive workloads - and may not address the availability-side concern identified by the original CVSS. On systems where FUSE filesystems are not operationally required, blacklisting the fuse kernel module ('echo blacklist fuse >> /etc/modprobe.d/fuse-blacklist.conf') removes the attack surface entirely, at the cost of disabling all FUSE-based filesystems including SSHFS, overlayfs-in-user-mode, and similar.

Same weakness CWE-908 – Use of Uninitialized Resource

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
Container suse/sl-micro/6.0/base-os-container:2.1.3-7.177 Container suse/sl-micro/6.1/base-os-container:2.2.1-5.155 Affected
Container suse/sl-micro/6.0/rt-os-container:2.1.3-7.206 Container suse/sl-micro/6.1/rt-os-container:2.2.1-5.152 Affected
Image SLES15-SP7-Azure-3P Image SLES15-SP7-Azure-Basic Image SLES15-SP7-Azure-Standard Image SLES15-SP7-HPC-Azure Affected
Image SLES15-SP7-BYOS-Azure Image SLES15-SP7-BYOS-GCE Image SLES15-SP7-CHOST-BYOS-Aliyun Image SLES15-SP7-CHOST-BYOS-Azure Image SLES15-SP7-CHOST-BYOS-EC2 Image SLES15-SP7-CHOST-BYOS-GCE Image SLES15-SP7-CHOST-BYOS-GDC Image SLES15-SP7-CHOST-BYOS-SAP-CCloud Image SLES15-SP7-EC2 Image SLES15-SP7-EC2-ECS-HVM Image SLES15-SP7-GCE Image SLES15-SP7-HPC-BYOS-Azure Image SLES15-SP7-HPC-BYOS-EC2 Image SLES15-SP7-HPC-BYOS-GCE Image SLES15-SP7-Hardened-BYOS-Azure Image SLES15-SP7-Hardened-BYOS-EC2 Image SLES15-SP7-Hardened-BYOS-GCE Image SLES15-SP7-SAPCAL-Azure Image SLES15-SP7-SAPCAL-EC2 Image SLES15-SP7-SAPCAL-GCE Affected
Image SLES15-SP7-SAP-Azure Image SLES15-SP7-SAP-Azure-3P Image SLES15-SP7-SAP-BYOS-Azure Image SLES15-SP7-SAP-BYOS-EC2 Image SLES15-SP7-SAP-BYOS-GCE Image SLES15-SP7-SAP-EC2 Image SLES15-SP7-SAP-GCE Image SLES15-SP7-SAP-Hardened-Azure Image SLES15-SP7-SAP-Hardened-BYOS-Azure Image SLES15-SP7-SAP-Hardened-BYOS-EC2 Image SLES15-SP7-SAP-Hardened-BYOS-GCE Image SLES15-SP7-SAP-Hardened-GCE Affected

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EUVD-2026-39258 vulnerability details – vuln.today
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