Incorrect calculation in Linux kernel - CVE-2026-64159

Vulnerability identifier: #VU138478

CSH Severity: Low

CVSS v4: 4.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-64159

CWE-ID: CWE-682

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to cause incorrect file reads.

The vulnerability exists due to improper handling of file size state in netfs_release_folio() when releasing a folio while uncommitted page cache data exists beyond the folio and the on-server EOF falls within that folio. A local user can trigger this condition through crafted file operations to cause incorrect file reads.

This was observed on cifs with the default cache option and no fscache.

Linux kernel
Ubuntu
linux-ibm (Ubuntu package)
linux-azure (Ubuntu package)
linux-aws (Ubuntu package)
linux-nvidia (Ubuntu package)
linux-nvidia-bos (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
linux-ibm (Ubuntu package) - addressed in versions 7.0.0-1008.8, 7.0.0-1010.10
linux-azure (Ubuntu package) - addressed in versions 7.0.0-1009.9, 7.0.0-1010.10
linux-aws (Ubuntu package) - addressed in versions 7.0.0-1009.9, 7.0.0-1015.15
linux-nvidia (Ubuntu package) - addressed in versions 7.0.0-1016.16, 7.0.0-1016.16~24.04.1
linux-nvidia-bos (Ubuntu package) - update to 7.0.0-2016.16

• https://git.kernel.org/stable/c/4543a4d737944134a1394afe797622546fbcc98a
• https://git.kernel.org/stable/c/5cd5207de519ef0c085f4f559adf5eefcb4c5202

• Incorrect calculation in Linux kernel netfs
• Ubuntu update for linux-ibm
• Ubuntu update for linux-azure
• Ubuntu update for linux-aws
• Ubuntu update for linux-nvidia-bos
• Ubuntu update for linux-nvidia