# CVE-2026-93254: arm64: entry: Avoid unnecessary local_irq_disable() on kernel exit

> A logic error in the Linux kernel arm64 entry path causes unnecessary IRQ disabling and potential warnings, potentially leading to system instability or denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Not stated
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-93254, GHSA-fh67-pc46-97cw, UBUNTU-CVE-2026-93254

## What is CVE-2026-93254?

CVE-2026-93254 is a denial of service vulnerability in Linux, published on 24 Sep 2026. 

### Official description

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

arm64: entry: Avoid unnecessary local_irq_disable() on kernel exit

Currently, when exiting to kernel mode, we attempt involuntary
preemption. The preemption logic expects IRQs to be disabled, which is
why we call local_irq_disable() before attempting preemption.

However, depending on the context, local_irq_disable() may be
unnecessary:

- __el1_irq(), the non-NMI EL1 IRQ path, already has IRQs disabled, so
  local_irq_disable() is redundant.

- irqentry_exit_to_kernel_mode_preempt() immediately returns when
  exiting from an NMI-like context, so calling local_irq_disable()
  beforehand is unnecessary work.

Furthermore, it confuses the pNMI state tracking when we are in a
context with interrupts disabled and the GIC_PRIO_PSR_I_SET bit is set
in the PMR, leading to a warning when
CONFIG_ARM64_DEBUG_PRIORITY_MASKING=y:

     WARNING: ./arch/arm64/include/asm/irqflags.h:63 at arm64_exit_to_kernel_mode+0xb8/0xc0, CPU#40: retsnoop/31805
     CPU: 40 UID: 0 PID: 31805 Comm: retsnoop Not tainted 7.2.0-rc6-next-20260805 #7 PREEMPTLAZY
     pstate: 234013c9 (nzCv DAIF +PAN -UAO +TCO +DIT +SSBS BTYPE=--)
     pc : arm64_exit_to_kernel_mode (arch/arm64/kernel/entry-common.c:63)
     lr : el1_abort (arch/arm64/kernel/entry-common.c:323)
     pmr: 000000f0
     Call trace:
      arm64_exit_to_kernel_mode (arch/arm64/kernel/entry-common.c:63) (P)
      el1_abort (arch/arm64/kernel/entry-common.c:323)
      el1h_64_sync_handler (arch/arm64/kernel/entry-common.c:449)
      el1h_64_sync (arch/arm64/kernel/entry.S:589)
      [...]

Split arm64_exit_to_kernel_mode() into preempt, non-preempt, and
dispatch parts so that we can avoid this extra work where it is not
needed and avoid breaking the pNMI tracking logic.

## Which versions are affected by CVE-2026-93254?


## How do I fix CVE-2026-93254?

Apply the vendor's patch.

## Is CVE-2026-93254 being exploited?

There is no known exploitation of CVE-2026-93254 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93254 and fix it if it is affected.

What it is: CVE-2026-93254 is a denial of service vulnerability in Linux, published on 24 Sep 2026. 
Exploitation: There is no known exploitation of CVE-2026-93254 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-2026-93254/ (Markdown: https://insights.sbomify.com/CVE-2026-93254/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93254
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93254
- OSV: https://osv.dev/vulnerability/CVE-2026-93254

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93254/
Summaries are generated and may contain mistakes; the official description above is the record.