CVE-2026-72183

Status: UPDATED  |  Advisory ID: CVE-2026-72183

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

landlock: Fix LANDLOCK_SCOPE_SIGNAL bypass on the SIGIO path

LANDLOCK_SCOPE_SIGNAL must prevent a sandboxed process from signaling

processes outside its Landlock domain. It can be bypassed through the

asynchronous SIGIO delivery path.

A sandboxed process that owns any file or socket can arm it with

fcntl(fd, F_SETOWN, -pgid), fcntl(fd, F_SETSIG, SIGKILL) and O_ASYNC, so

that an I/O event makes the kernel deliver the chosen signal to the

whole process group. As the head of its process group's task list (the

default position right after fork()) that group can also hold the

non-sandboxed process that launched it, e.g. a supervisor or a security

monitor. The sandbox can thus kill or signal the processes

LANDLOCK_SCOPE_SIGNAL is meant to protect from it.

The scope is enforced in hook_file_send_sigiotask() against the Landlock

domain recorded at F_SETOWN time, not the live domain of the sender.

control_current_fowner() decides whether to record that domain and skips

recording it when the fowner target is in the caller's thread group,

which is safe only for a single-task target (PIDTYPE_PID, PIDTYPE_TGID).

For a process group (PIDTYPE_PGID) pid_task() returns only one member;

recording is skipped whenever that member shares the caller's thread

group, and hook_file_send_sigiotask() then lets the signal fan out to

the whole group unchecked.

Record the domain for every non single-process target so the scope is

enforced against each group member at delivery time.

That recording is necessary but not sufficient on its own: the kernel

signals a process group through its members' thread-group leaders, and

the leader of the registrant's own process can carry a different

Landlock domain than the sibling thread that armed the owner.

domain_is_scoped() would then deny that leader, even though commit

18eb75f3af40 ("landlock: Always allow signals between threads of the

same process") requires same-process delivery to be allowed.

hook_task_kill() avoids this by evaluating same_thread_group() live, per

recipient; the SIGIO path instead delegates the whole decision to a

single registration-time check, which a process-group fan-out cannot

honor.

So also record the registrant's thread group next to its domain and

exempt it at delivery: hook_file_send_sigiotask() allows the signal

whenever the recipient belongs to the registrant's own process,

restoring the same-process guarantee while keeping out-of-domain group

members blocked. The direct kill() path (hook_task_kill) already

evaluates the live domain and is unaffected.

[mic: Check pid_type earlier and improve comment, fix commit message,

fix comment formatting] (NVD)

What to Do

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

References