CVE-2026-64496 iio: event: Fix event FIFO reset race

What is CVE-2026-64496?

CVE-2026-64496 is a high-severity vulnerability in Linux, published on 25 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

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

iio: event: Fix event FIFO reset race

`iio_event_getfd()` creates the event file descriptor with `anon_inode_getfd()`, which allocates a new fd, creates the anonymous file and installs it in the process fd table before returning to the caller.

The IIO code resets the event FIFO after `anon_inode_getfd()` has returned, but before `IIO_GET_EVENT_FD_IOCTL` has copied the fd number to userspace. But since fd tables are shared between threads, another thread can guess the newly allocated fd number and issue a `read()` on it as soon as the fd has been installed.

This means the `kfifo_to_user()` in `iio_event_chrdev_read()` can run in parallel with the `kfifo_reset_out()` in `iio_event_getfd()`.

The kfifo documentation says that `kfifo_reset_out()` is only safe when it is called from the reader thread and there is only one concurrent reader. Otherwise it is dangerous and must be handled in the same way as `kfifo_reset()`.

If that happens, `kfifo_to_user()` can advance the FIFO `out` index based on state from before the reset, after the reset has already moved the `out` index to the current `in` index. That can leave the FIFO with an `out` index past the `in` index. A later `read()` can then see an underflowed FIFO length and copy more data than the event FIFO buffer contains. This can result in an out-of-bounds read and leak adjacent kernel memory to userspace.

Move the FIFO reset before `anon_inode_getfd()`. At that point the event fd is marked busy, but the new fd has not been installed yet, so userspace cannot access it while the FIFO is reset.

Weakness: CWE-362

Which versions are affected by CVE-2026-64496?

How do I fix CVE-2026-64496?

Apply the vendor's patch.

Is CVE-2026-64496 being exploited?

There is no known exploitation of CVE-2026-64496 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as ALSA-2026:52761, ALSA-2026:52765, AZL-93731, BELL-CVE-2026-64496, DEBIAN-CVE-2026-64496, GHSA-hh3r-jgc6-qr6q and 7 more.