CVE-2026-43106

/* * PoC for CVE-2026-43106: cachefiles dentry refcount issue * This code conceptually triggers the vulnerable path. * Note: Exploiting kernel vulnerabilities requires a specific environment. */ #include <stdio.h> #include <stdlib.h> #include <fcntl.h> #include <unistd.h> #include <sys/stat.h> // Conceptual trigger for cachefiles_cull() void trigger_vulnerability() { // Setup: Ensure cachefiles is enabled and a cache is bound. // The vulnerability occurs when the kernel tries to cull an object. int fd = open("/tmp/cachefiles_test", O_RDWR | O_CREAT, 0644); if (fd < 0) { perror("Failed to open file"); return; } printf("Attempting to trigger cachefiles_cull logic...\n"); // In a real scenario, one would interact with the cachefiles daemon // or manipulate the filesystem to force a cull operation on a dentry // that is in the specific state required to hit the bug. // Simulate interaction that leads to cull write(fd, "test data", 9); close(fd); // The kernel internal function cachefiles_cull() would be called // leading to the refcount drop in cachefiles_bury_object(). } int main() { printf("CVE-2026-43106 PoC Trigger\n"); trigger_vulnerability(); return 0; }

{"cve": {"id": "CVE-2026-43106", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-06T10:16:24.213", "lastModified": "2026-05-11T17:31:12.830", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncachefiles: fix incorrect dentry refcount in cachefiles_cull()\n\nThe patch mentioned below changed cachefiles_bury_object() to expect 2\nreferences to the 'rep' dentry. Three of the callers were changed to\nuse start_removing_dentry() which takes an extra reference so in those\ncases the call gets the expected references.\n\nHowever there is another call to cachefiles_bury_object() in\ncachefiles_cull() which did not need to be changed to use\nstart_removing_dentry() and so was not properly considered.\nIt still passed the dentry with just one reference so the net result is\nthat a reference is lost.\n\nTo meet the expectations of cachefiles_bury_object(), cachefiles_cull()\nmust take an extra reference before the call. It will be dropped by\ncachefiles_bury_object()."}], "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:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "NVD-CWE-Other"}]}], "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/1635c2acdde86c4f555b627aec873c8677c421ed", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/6577df7dc7a7de128442b6192c7a32195c923480", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}