# CVE-2026-89750

## Summary

- **CVE ID:** CVE-2026-89750
- **Severity:** HIGH
- **CVSS Score:** 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
- **CWE:** N/A
- **Published:** Sep 11, 2026
- **Last Modified:** Sep 14, 2026

## Description

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

tracing/user_events: Clear copied tracing state before fork duplication

dup_task_struct() copies user_event_mm from the parent into the child,
without grabbing a reference to it. user_event_mm_dup() should
replace it, but it leaves that copied pointer unmodified if
user_event_mm_alloc() fails.

When the child exits, user_event_mm_remove() decrements a reference
the child never owned, which ultimately frees user_event_mm, while
the parent still as a stale pointer to it. This creates a UAF, which
KASAN reports as:

    BUG: KASAN: slab-use-after-free in
    current_user_event_mm+0x51/0x1d0 Write of size 4 at addr
    ffff888005010d30 by task init/44

    Call Trace:
     <TASK>
     kasan_report+0xce/0x100
     kasan_check_range+0x10f/0x1e0
     current_user_event_mm+0x51/0x1d0
     user_events_ioctl+0x82e/0x15c0
     __x64_sys_ioctl+0x139/0x1c0
     do_syscall_64+0xce/0x450
     entry_SYSCALL_64_after_hwframe+0x77/0x7f

    Allocated by task 44:
     __kasan_kmalloc+0x8f/0xa0
     __kmalloc_cache_noprof+0x180/0x3a0
     user_event_mm_alloc+0x3c/0x1f0
     current_user_event_mm+0x88/0x1d0

    Freed by task 42:
     __kasan_slab_free+0x43/0x70
     kfree+0x13a/0x390
     process_one_work+0x696/0xf90
     worker_thread+0x420/0xba0

The fix simply clears the copied pointer before any possible failure.
In case of failure, the child then has nothing to free.

## Affected Products

- Linux — Linux (7235759084a4f8524a46bd2638885ff3b34ce279)
- Linux — Linux (6.4)
- Linux — Linux (0)
- Linux — Linux (6.12.109)
- Linux — Linux (6.18.50)
- Linux — Linux (7.2.4)
- Linux — Linux (7.3-rc1)
- Linux — Linux (6.6.157)

## References

- [CNA](https://git.kernel.org/stable/c/63b39e49a4c9d68e010e96b26fc7374f0864f2b1)
- [CNA](https://git.kernel.org/stable/c/25a0758cf6bdbfddac2be71124c9bd0692f4b0b1)
- [CNA](https://git.kernel.org/stable/c/b799f67119aff179719a0b1e12441ebbdaaf62f9)
- [CNA](https://git.kernel.org/stable/c/390f6bd8583d177029d9df4bea6667509e55a765)
- [CNA](https://git.kernel.org/stable/c/33ce55b368b64d65941867add00e7f288cbb8234)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.16%
- **EPSS Percentile:** 5.4

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-18._