CVE-2026-99203

Status: UPDATED  |  Advisory ID: CVE-2026-99203

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

pipe: preserve existing fasync readers on writer setup failure

F_SETFL and FIOASYNC decide whether to invoke ->fasync() before

pipe_fasync() takes pipe->mutex. Two enables of one O_RDWR FIFO can

therefore both enter the callback.

fasync_helper() allocates before checking for an existing entry. If the

first enable installs both entries, a second enable can update the

reader entry and then fail the allocation for the writer entry. The

error path removes the pre-existing reader entry, clearing FASYNC while

the writer entry remains registered. __fput() then skips ->fasync(), so a

later pipe notification can dereference the freed file or its f_owner.

An unprivileged memory-pressure reproducer triggers a KASAN

slab-use-after-free in send_sigio() through this path.

Keep the reader helper's result and undo the registration only if this

call added it. The pipe mutex serializes changes to both lists, so a

failed new registration still removes its reader, while a failed

duplicate preserves the existing registrations and FASYNC. Successful

duplicate enables continue to update fa_fd as before. (NVD)

What to Do

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

References