Use-after-free in Linux kernel - CVE-2026-98921

Vulnerability identifier: #VU157590

CSH Severity: Low

CVSS v4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-98921

CWE-ID: CWE-416

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to potentially cause a denial of service by triggering invalid kernel memory access.

The vulnerability exists due to use-after-free in the OverlayFS ovl_do_mkdir() debug logging when formatting an input dentry after vfs_mkdir() has freed or replaced it. A local user can trigger an affected directory creation operation to potentially crash the kernel.

The vulnerable debug logging is enabled when CONFIG_OVERLAY_FS_DEBUG is enabled.

Linux kernel
Ubuntu
linux (Ubuntu package)
linux-aws (Ubuntu package)
linux-gcp (Ubuntu package)
linux-oracle (Ubuntu package)
linux-ibm (Ubuntu package)
linux-hwe-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
linux (Ubuntu package) - update to 7.0.0-42.42
linux-aws (Ubuntu package) - update to 7.0.0-1016.17
linux-gcp (Ubuntu package) - update to 7.0.0-1016.18
linux-oracle (Ubuntu package) - update to 7.0.0-1015.16
linux-ibm (Ubuntu package) - update to 7.0.0-1017.17
linux-hwe-7.0 (Ubuntu package) - update to 7.0.0-42.42~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1017.17

• https://git.kernel.org/stable/c/719bd33ab359c539a68a278c15a97deb77565cdb
• https://git.kernel.org/stable/c/ae146bc1abdeb4607abf2975b858c053024e8ac1

• Use-after-free in Linux kernel overlayfs
• Ubuntu update for linux-oem-7.0
• Ubuntu update for linux, linux-aws, linux-gcp and more