# CVE-2026-89750: tracing/user_events: Clear copied tracing state before fork duplication

CVE-2026-89750 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-89750, released September 23, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-89750
- Priority: High
- CVSS: 7.8 (Important)
- EPSS: 0.0016
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 11, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-89750

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.12.111-1 | [DEBIAN-CVE-2026-89750](https://patchblox.com/security/data/fix/linux/debian-cve-2026-89750.md) | Sep 23, 2026 |
| Linux | linux Debian 14 | 7.2.6-1 | [DEBIAN-CVE-2026-89750](https://patchblox.com/security/data/fix/linux/debian-cve-2026-89750.md) | Sep 23, 2026 |
| Linux | linux-6.12 Debian 12.15 (bookworm) | 6.12.111-1~deb12u1 | [DEBIAN-CVE-2026-89750](https://patchblox.com/security/data/fix/linux/debian-cve-2026-89750.md) | Sep 23, 2026 |

---

Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data

Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.