SB2026102404 - Use-after-free in Linux kernel overlayfs

Description

This security bulletin contains information about 1 vulnerability.

1) Use-after-free (CVE-ID: CVE-2026-98921)

CWE-ID: CWE-416 - Use After Free

CVSSv4: 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]

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.

Remediation

Install update from vendor's website.

References

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