{"id":"CVE-2026-63808","revision":"542d96b859e14cfdb024f4c4ca636101","records":[{"revision":"542d96b859e14cfdb024f4c4ca636101","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-63808","aliases":[],"title":"exfat: fix potential use-after-free in exfat_find_dir_entry()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nexfat: fix potential use-after-free in exfat_find_dir_entry()\n\nIn exfat_find_dir_entry(), the buffer_head obtained from\nexfat_get_dentry() is released with brelse(bh) before the fall-through\nTYPE_EXTEND branch reads the directory entry through ep (which points\ninto bh->b_data):\n\n\tbrelse(bh);\n\tif (entry_type == TYPE_EXTEND) {\n\t\t...\n\t\tlen = exfat_extract_uni_name(ep, entry_uniname);\n\t\t...\n\t}\n\nAfter brelse() drops our reference, nothing guarantees that the\nunderlying page backing bh->b_data remains valid for the subsequent\nexfat_extract_uni_name() read. This is the same pattern fixed in\ncommit fc961522ddbd (\"exfat: Fix potential use after free in\nexfat_load_upcase_table()\").\n\nMove brelse(bh) so it runs after ep is no longer dereferenced on\neach branch.\n\nConfirmed on QEMU x86_64 with CONFIG_KASAN=y + CONFIG_DEBUG_PAGEALLOC=y\n+ CONFIG_PAGE_POISONING=y on linux-next, using a crafted exFAT image\n(long filename with same-hash collisions forcing the TYPE_EXTEND path).\nWith a debug-only invalidate_bdev() inserted between brelse(bh) and\nthe ep read to make the stale-deref window deterministic, the\nunpatched kernel faults:\n\n  BUG: KASAN: use-after-free in exfat_find_dir_entry+0x133b/0x15a0\n  BUG: unable to handle page fault for address: ffff88801a5fa0c2\n  Oops: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI\n  RIP: 0010:exfat_find_dir_entry+0x1188/0x15a0\n\nWith this patch applied, the same instrumented harness completes\ncleanly under the same sanitizer stack. I have not reproduced a\ncrash on an uninstrumented kernel under ordinary reclaim; the\ninstrumented A/B establishes the lifetime violation and that the\npatch closes it, not an unaided triggerability claim.","state":0,"publishedAt":"2026-07-19T12:02:11.323+00:00","modifiedAt":"2026-10-19T20:07:48.432+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"fs/exfat/dir.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"ca06197382bde0a3bc20215595d1c9ce20c6e341\",\n                            \"lessThan\": \"e6f1a11cfb808441a43ffae9b476cc135732cd27\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"ca06197382bde0a3bc20215595d1c9ce20c6e341\",\n                            \"lessThan\": \"e48f413c2815787b8cade2795e194e3c4cd782ef\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"ca06197382bde0a3bc20215595d1c9ce20c6e341\",\n                            \"lessThan\": \"06c4e1e9967d332ac33ba38b7819851089ff9359\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"ca06197382bde0a3bc20215595d1c9ce20c6e341\",\n                            \"lessThan\": \"8e0abc17fbd7e305802e84fe98b4950d50f9c433\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"ca06197382bde0a3bc20215595d1c9ce20c6e341\",\n                            \"lessThan\": \"4d101016d5e587f820b3ae2d5bb6770d86342649\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"ca06197382bde0a3bc20215595d1c9ce20c6e341\",\n                            \"lessThan\": \"adfacfbaeae2cb760f492357cc36b41f84ef7f86\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"ca06197382bde0a3bc20215595d1c9ce20c6e341\",\n                            \"lessThan\": \"708b97e792945d3e4653939fd3405d71a61ad065\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"ca06197382bde0a3bc20215595d1c9ce20c6e341\",\n                            \"lessThan\": \"3f5f8ee9917cc2b9076ac533492d8a200edcabb8\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"fs/exfat/dir.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"5.7\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"5.7\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.10.260\",\n                            \"lessThanOrEqual\": \"5.10.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.15.211\",\n                            \"lessThanOrEqual\": \"5.15.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.177\",\n                            \"lessThanOrEqual\": \"6.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.144\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.95\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.38\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.1.3\",\n                            \"lessThanOrEqual\": \"7.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8,"severity":"CRITICAL"}],"references":["https://git.kernel.org/stable/c/e6f1a11cfb808441a43ffae9b476cc135732cd27","https://git.kernel.org/stable/c/e48f413c2815787b8cade2795e194e3c4cd782ef","https://git.kernel.org/stable/c/06c4e1e9967d332ac33ba38b7819851089ff9359","https://git.kernel.org/stable/c/8e0abc17fbd7e305802e84fe98b4950d50f9c433","https://git.kernel.org/stable/c/4d101016d5e587f820b3ae2d5bb6770d86342649","https://git.kernel.org/stable/c/adfacfbaeae2cb760f492357cc36b41f84ef7f86","https://git.kernel.org/stable/c/708b97e792945d3e4653939fd3405d71a61ad065","https://git.kernel.org/stable/c/3f5f8ee9917cc2b9076ac533492d8a200edcabb8"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-63808","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-63808","identifiers":["CVE-2026-63808"]},"retained":false,"historicalAffected":[]}],"coverage":[]}