CVE-2026-93256 arm64: hibernate: mask DAIF before restoring hibernated kernel
A flaw in Linux kernel arm64 hibernation resume allows fatal crashes or warnings due to improper exception masking, requiring local access to trigger.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-93256?
CVE-2026-93256 is a denial of service vulnerability in Linux, published on 24 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:
arm64: hibernate: mask DAIF before restoring hibernated kernel
The arm64 hibernate code manages the exception masking in an unsound way, leading to potential crashes and/or warnings during resume.
When a hibernation image is saved in `swsusp_arch_suspend()`, all DAIF exceptions are masked (by virtue of `local_daif_save()`), and the suspended image is saved assuming that all DAIF exceptions will remain masked when the image is restored.
When a hibernation image is resumed by `swsusp_arch_resume()`, only interrupts are masked (by virtue of `local_irq_disable()` in `resume_target_kernel()`). When pseudo-NMI is enabled the DAIF.IF bits will be clear, and regardless of pseudo-NMI the DAIF.DA bits will be clear.
This means that there are two problems:
(1) It is possible to take Debug, SError, or pseudo-NMI exceptions during the resume process. This is unsafe, as during the resume process both the old ane new kernels will tranisently be in an inconsistent state, and swsusp_arch_suspend_exit() won't retain an executable mapping of any exception vectors.
Any exception taken here will be fatal and silent.
(2) When re-entering the resumed kernel, some DAIF bits will be clear unexpectedly. This permits Debug, SError, or pseudo-NMI exceptions to be taken for a short period while the resumed kernel is not yet in a consistent state.
This is detected by CONFIG_ARM64_DEBUG_PRIORITY_MASKING.
Avoid these issues by masking all DAIF exceptions during resume.
Which versions are affected by CVE-2026-93256?
How do I fix CVE-2026-93256?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-93256 being exploited?
There is no known exploitation of CVE-2026-93256 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-93256, DEBIAN-CVE-2026-93256, GHSA-jf3q-gp4f-qwvj, UBUNTU-CVE-2026-93256.