# CVE-2025-37936: perf/x86/intel: KVM: Mask PEBS_ENABLE loaded for guest with vCPU's value. > A flaw in Linux kernel KVM allows unexpected PEBS enablement in guests, causing crashes via page faults when profiling is active. - **Severity:** High 8.7 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/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:** 20 May 2025 - **Updated:** 15 Oct 2026 - **Also known as:** BELL-CVE-2025-37936, DEBIAN-CVE-2025-37936, GHSA-7qvj-8m4h-6v7j, ROOT-OS-DEBIAN-12-CVE-2025-37936, ROOT-OS-UBUNTU-2404-CVE-2025-37936, UBUNTU-CVE-2025-37936 ## What is CVE-2025-37936? CVE-2025-37936 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 20 May 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: perf/x86/intel: KVM: Mask PEBS_ENABLE loaded for guest with vCPU's value. When generating the MSR_IA32_PEBS_ENABLE value that will be loaded on VM-Entry to a KVM guest, mask the value with the vCPU's desired PEBS_ENABLE value. Consulting only the host kernel's host vs. guest masks results in running the guest with PEBS enabled even when the guest doesn't want to use PEBS. Because KVM uses perf events to proxy the guest virtual PMU, simply looking at exclude_host can't differentiate between events created by host userspace, and events created by KVM on behalf of the guest. Running the guest with PEBS unexpectedly enabled typically manifests as crashes due to a near-infinite stream of #PFs. E.g. if the guest hasn't written MSR_IA32_DS_AREA, the CPU will hit page faults on address '0' when trying to record PEBS events. The issue is most easily reproduced by running `perf kvm top` from before commit 7b100989b4f6 ("perf evlist: Remove __evlist__add_default") (after which, `perf kvm top` effectively stopped using PEBS). The userspace side of perf creates a guest-only PEBS event, which intel_guest_get_msrs() misconstrues a guest-*owned* PEBS event. Arguably, this is a userspace bug, as enabling PEBS on guest-only events simply cannot work, and userspace can kill VMs in many other ways (there is no danger to the host). However, even if this is considered to be bad userspace behavior, there's zero downside to perf/KVM restricting PEBS to guest-owned events. Note, commit 854250329c02 ("KVM: x86/pmu: Disable guest PEBS temporarily in two rare situations") fixed the case where host userspace is profiling KVM *and* userspace, but missed the case where userspace is profiling only KVM. ## Which versions are affected by CVE-2025-37936? It affects 2 products. Products: Debian Debian Linux, Linux kernel. ## How do I fix CVE-2025-37936? Apply the vendor's patch. ## Is CVE-2025-37936 being exploited? There is no known exploitation of CVE-2025-37936 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-2025-37936 and fix it if it is affected. What it is: CVE-2025-37936 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 20 May 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-2025-37936 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-2025-37936/ (Markdown: https://insights.sbomify.com/CVE-2025-37936/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2025-37936 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-37936 - OSV: https://osv.dev/vulnerability/CVE-2025-37936 --- From sbomify Insights: https://insights.sbomify.com/CVE-2025-37936/ Summaries are generated and may contain mistakes; the official description above is the record.