{"id":"CVE-2025-21779","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86: Reject Hyper-V's SEND_IPI hypercalls if local APIC isn't in-kernel\n\nAdvertise support for Hyper-V's SEND_IPI and SEND_IPI_EX hypercalls if and\nonly if the loc…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86: Reject Hyper-V's SEND_IPI hypercalls if local APIC isn't in-kernel\n\nAdvertise support for Hyper-V's SEND_IPI and SEND_IPI_EX hypercalls if and\nonly if the loc…","severity":"medium","cvss":5.5,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-476"],"vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 4.20, < 6.1.129","linux_kernel >= 6.2, < 6.6.79","linux_kernel >= 6.7, < 6.12.16","linux_kernel >= 6.13, < 6.13.4","linux_kernel = 6.14"],"patched":["linux_kernel 6.13.4"],"published":"2025-02-27","updated":"2026-10-15","sourceUpdated":"2026-10-15T02:17:35.043","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2025-21779","references":[{"url":"https://git.kernel.org/stable/c/45fa526b0f5a34492ed0536c3cdf88b78380e4de","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/5393cf22312418262679eaadb130d608c75fe690","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/61224533f2b61e252b03e214195d27d64b22989a","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/874ff13c73c45ecb38cb82191e8c1d523f0dc81b","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a8de7f100bb5989d9c3627d3a223ee1c863f3b69","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/aca8be4403fb90db7adaf63830e27ebe787a76e8","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ca29f58ca374c40a0e69c5306fc5c940a0069074","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-784472.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}],"tags":["nvd","cve.org"],"epss":0.00251,"epssPercentile":0.16421,"ingestedAt":"2026-10-15T03:30:12.796Z","slug":"CVE-2025-21779","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86: Reject Hyper-V's SEND_IPI hypercalls if local APIC isn't in-kernel\n\nAdvertise support for Hyper-V's SEND_IPI and SEND_IPI_EX hypercalls if and\nonly if the local API is emulated/virtualized by KVM, and explicitly reject\nsaid hypercalls if the local APIC is emulated in userspace, i.e. don't rely\non userspace to opt-in to KVM_CAP_HYPERV_ENFORCE_CPUID.\n\nRejecting SEND_IPI and SEND_IPI_EX fixes a NULL-pointer dereference if\nHyper-V enlightenments are exposed to the guest without an in-kernel local\nAPIC:\n\n  dump_stack+0xbe/0xfd\n  __kasan_report.cold+0x34/0x84\n  kasan_report+0x3a/0x50\n  __apic_accept_irq+0x3a/0x5c0\n  kvm_hv_send_ipi.isra.0+0x34e/0x820\n  kvm_hv_hypercall+0x8d9/0x9d0\n  kvm_emulate_hypercall+0x506/0x7e0\n  __vmx_handle_exit+0x283/0xb60\n  vmx_handle_exit+0x1d/0xd0\n  vcpu_enter_guest+0x16b0/0x24c0\n  vcpu_run+0xc0/0x550\n  kvm_arch_vcpu_ioctl_run+0x170/0x6d0\n  kvm_vcpu_ioctl+0x413/0xb20\n  __se_sys_ioctl+0x111/0x160\n  do_syscal1_64+0x30/0x40\n  entry_SYSCALL_64_after_hwframe+0x67/0xd1\n\nNote, checking the sending vCPU is sufficient, as the per-VM irqchip_mode\ncan't be modified after vCPUs are created, i.e. if one vCPU has an\nin-kernel local APIC, then all vCPUs have an in-kernel local APIC.\n\n## Affected\n\n- `linux_kernel >= 4.20, < 6.1.129`\n- `linux_kernel >= 6.2, < 6.6.79`\n- `linux_kernel >= 6.7, < 6.12.16`\n- `linux_kernel >= 6.13, < 6.13.4`\n- `linux_kernel = 6.14`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 6.13.4`","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":30.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}