# CVE-2025-38670: arm64/entry: Mask DAIF in cpu_switch_to(), call_on_irq_stack() > A race condition in the Linux kernel arm64 entry code can cause stack corruption and kernel panics, particularly when pseudo-NMIs are enabled. - **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Local or same network only - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 22 Aug 2025 - **Updated:** 5 Aug 2026 - **Also known as:** AZL-66656, AZL-75093, BELL-CVE-2025-38670, DEBIAN-CVE-2025-38670, GHSA-6v6p-g835-47x6, ROOT-OS-DEBIAN-12-CVE-2025-38670, ROOT-OS-DEBIAN-13-CVE-2025-38670, ROOT-OS-UBUNTU-2204-CVE-2025-38670, ROOT-OS-UBUNTU-2404-CVE-2025-38670, UBUNTU-CVE-2025-38670 ## What is CVE-2025-38670? CVE-2025-38670 is a high-severity vulnerability in Debian Debian Linux, published on 22 Aug 2025. 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/entry: Mask DAIF in cpu_switch_to(), call_on_irq_stack() `cpu_switch_to()` and `call_on_irq_stack()` manipulate SP to change to different stacks along with the Shadow Call Stack if it is enabled. Those two stack changes cannot be done atomically and both functions can be interrupted by SErrors or Debug Exceptions which, though unlikely, is very much broken : if interrupted, we can end up with mismatched stacks and Shadow Call Stack leading to clobbered stacks. In `cpu_switch_to()`, it can happen when SP_EL0 points to the new task, but x18 stills points to the old task's SCS. When the interrupt handler tries to save the task's SCS pointer, it will save the old task SCS pointer (x18) into the new task struct (pointed to by SP_EL0), clobbering it. In `call_on_irq_stack()`, it can happen when switching from the task stack to the IRQ stack and when switching back. In both cases, we can be interrupted when the SCS pointer points to the IRQ SCS, but SP points to the task stack. The nested interrupt handler pushes its return addresses on the IRQ SCS. It then detects that SP points to the task stack, calls `call_on_irq_stack()` and clobbers the task SCS pointer with the IRQ SCS pointer, which it will also use ! This leads to tasks returning to addresses on the wrong SCS, or even on the IRQ SCS, triggering kernel panics via CONFIG_VMAP_STACK or FPAC if enabled. This is possible on a default config, but unlikely. However, when enabling CONFIG_ARM64_PSEUDO_NMI, DAIF is unmasked and instead the GIC is responsible for filtering what interrupts the CPU should receive based on priority. Given the goal of emulating NMIs, pseudo-NMIs can be received by the CPU even in `cpu_switch_to()` and `call_on_irq_stack()`, possibly *very* frequently depending on the system configuration and workload, leading to unpredictable kernel panics. Completely mask DAIF in `cpu_switch_to()` and restore it when returning. Do the same in `call_on_irq_stack()`, but restore and mask around the branch. Mask DAIF even if CONFIG_SHADOW_CALL_STACK is not enabled for consistency of behaviour between all configurations. Introduce and use an assembly macro for saving and masking DAIF, as the existing one saves but only masks IF. Weakness: CWE-668 (Exposure of Resource to Wrong Sphere) ## Which versions are affected by CVE-2025-38670? It affects 2 products. Products: Debian Debian Linux, Linux kernel. ## How do I fix CVE-2025-38670? Apply the vendor's patch. ## Is CVE-2025-38670 being exploited? There is no known exploitation of CVE-2025-38670 in the wild and no public exploit code. ## Other vulnerabilities in Debian Debian Linux - [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild) - [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild) - [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild) - [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild) - [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2025-38670 and fix it if it is affected. What it is: CVE-2025-38670 is a high-severity vulnerability in Debian Debian Linux, published on 22 Aug 2025. 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-2025-38670 in the wild and no public exploit code. Affected product: Debian Debian 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-2025-38670/ (Markdown: https://insights.sbomify.com/CVE-2025-38670/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2025-38670 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-38670 - OSV: https://osv.dev/vulnerability/CVE-2025-38670 --- From sbomify Insights: https://insights.sbomify.com/CVE-2025-38670/ Summaries are generated and may contain mistakes; the official description above is the record.