# CVE-2026-90305: ARM: 9483/1: select HAVE_POSIX_CPU_TIMERS_TASK_WORK

> A missing kernel configuration on ARM PREEMPT_RT systems causes a kernel panic when CPU timers expire, leading to local denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-90305, GHSA-8p49-rxqc-9388, UBUNTU-CVE-2026-90305

## What is CVE-2026-90305?

CVE-2026-90305 is a denial of service vulnerability in Linux, published on 17 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

ARM: 9483/1: select HAVE_POSIX_CPU_TIMERS_TASK_WORK

Commit c6e61c06d606 ("ARM: 9463/1: Allow to enable RT") enabled PREEMPT_RT
on ARM but did not select HAVE_POSIX_CPU_TIMERS_TASK_WORK. This leaves
CONFIG_POSIX_CPU_TIMERS_TASK_WORK disabled, so CPU timers expire in hard
IRQ context.

On PREEMPT_RT this makes run_posix_cpu_timers() take the sleeping
sighand->siglock:

  BUG: sleeping function called from invalid context at spinlock_rt.c:48
    rt_spin_lock from lock_task_sighand
    lock_task_sighand from run_posix_cpu_timers
    run_posix_cpu_timers from update_process_times

ARM handles TIF_NOTIFY_RESUME on all return-to-user paths, including v7-M.
ARM32 KVM host support was removed by commit 541ad0150ca4 ("arm: Remove
32bit KVM host support"), so the select need not be conditional on KVM.

Select it to defer POSIX CPU timer expiry to task context.

Reproduced with setrlimit(RLIMIT_CPU, ...) and a busy loop. The same path
is used by setitimer(ITIMER_PROF or ITIMER_VIRTUAL) and POSIX CPU timers
created with timer_create().

## Which versions are affected by CVE-2026-90305?


## How do I fix CVE-2026-90305?

Apply the vendor's patch.

## Is CVE-2026-90305 being exploited?

There is no known exploitation of CVE-2026-90305 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90305 and fix it if it is affected.

What it is: CVE-2026-90305 is a denial of service vulnerability in Linux, published on 17 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-90305 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-90305/ (Markdown: https://insights.sbomify.com/CVE-2026-90305/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90305
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90305
- OSV: https://osv.dev/vulnerability/CVE-2026-90305

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90305/
Summaries are generated and may contain mistakes; the official description above is the record.