CVE-2026-89600

Status: UPDATED  |  Advisory ID: CVE-2026-89600

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

fanotify: fix use-after-free of file range info

fsnotify_pre_content() builds its file_range on the triggering task's

stack. fanotify_alloc_perm_event() saves a pointer to range.pos in the

heap-allocated permission event so copy_range_info_to_user() can report

the offset later.

The event reader can set the event state to FAN_EVENT_REPORTED and then

sleep while preparing the file descriptor. If a signal interrupts the

triggering task at that point, fanotify_get_response() changes the state

to FAN_EVENT_CANCELED and returns. This unwinds the file_range stack

frame while the reader still owns the event. The reader then dereferences

pevent->ppos and copies the stale stack value to userspace.

KASAN reported:

BUG: KASAN: use-after-free in fanotify_read+0x293e/0x2970

Read of size 8 at addr ffff88811434fc50 by task fanotify_inotif/95

Call Trace:

fanotify_read+0x293e/0x2970

vfs_read+0x177/0xa20

ksys_read+0xf7/0x1c0

do_syscall_64+0xf9/0x540

entry_SYSCALL_64_after_hwframe+0x77/0x7f

Store the range position directly in the permission event and use

FANOTIFY_NO_RANGE when range information is unavailable. The event remains

alive until the reader finishes, so the reported offset no longer depends

on the triggering task's stack. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References