{"id":"CVE-2026-92499","summary":"ext4: validate readdir offset before accessing dirent","details":"In the Linux kernel, the following vulnerability has been resolved:\n\next4: validate readdir offset before accessing dirent\n\nA corrupted directory can trigger the following KASAN report when\next4_readdir() resumes from an invalid position:\n\n  BUG: KASAN: use-after-free in __ext4_check_dir_entry+0x5ef/0x820\n  Read of size 2 at addr ffff88810a646000 by task repro_linear/509\n\n  Call Trace:\n   \u003cTASK\u003e\n   dump_stack_lvl+0x53/0x70\n   print_report+0xd0/0x630\n   kasan_report+0xce/0x100\n   __ext4_check_dir_entry+0x5ef/0x820\n   ext4_readdir+0xcde/0x2b70\n   iterate_dir+0x1a1/0x520\n   __x64_sys_getdents64+0x12b/0x220\n   do_syscall_64+0xf9/0x540\n   entry_SYSCALL_64_after_hwframe+0x77/0x7f\n   \u003c/TASK\u003e\n\nKASAN reports use-after-free because the out-of-bounds access lands in an\nadjacent freed page. The directory buffer itself is still referenced.\n\next4_dir_llseek() invalidates the directory cookie so that ext4_readdir()\nrescans directory entries from the start of the block. The rescan checks\nonly the lower bound of rec_len before advancing. A corrupted rec_len can\ntherefore place the offset where the block has insufficient space for a\ncomplete directory entry. The rescan itself may dereference that truncated\nentry, or the main loop may pass it to __ext4_check_dir_entry(). The latter\nreads de-\u003erec_len before validating the range. For example:\n\n  block offset  0                           4092  4096\n                |---- de1.rec_len = 4092 -----|----|\n                                               de2.inode\n                                                    | de2.rec_len\n                                                    ^ OOB, reported as UAF\n\nde2 starts at offset 4092 in this 4 KiB block. Its four-byte inode fits in\nthe block, but its rec_len starts at offset 4096 and crosses the boundary.\n\nThe minimum safe length is inode-dependent. Encrypted and casefolded\ndirectory entries need eight additional hash bytes, while a valid metadata\nchecksum tail is only 12 bytes.\n\nCache the metadata checksum feature state and derive the minimum directory\nentry length from the on-disk format. Use it to bound both the rescan and\nthe offset passed to the main loop. Report an offset in a truncated block\ntail and skip the remainder of the block, while continuing to accept an\noffset exactly at the block boundary.","modified":"2026-09-19T03:47:26.500255870Z","published":"2026-09-17T16:10:13.391Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/92xxx/CVE-2026-92499.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/64d445d40e5ea4c4d4d88880db753b370cb69161"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b4c728577933753180e3e97f08424d5bcaff705e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/bc4b7b0414c33b2c8898eb04386df0d21a13dad8"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/92xxx/CVE-2026-92499.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-92499"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"ac27a0ec112a089f1a5102bc8dffc79c8c815571"},{"fixed":"64d445d40e5ea4c4d4d88880db753b370cb69161"},{"fixed":"b4c728577933753180e3e97f08424d5bcaff705e"},{"fixed":"bc4b7b0414c33b2c8898eb04386df0d21a13dad8"}]}],"versions":["v7.2.5","v6.18.51","v7.2.4","v6.18.50","v7.2.3","v6.18.49","v7.2.2","v6.18.48","v7.2","v7.2.1","v6.18.47","v6.18.46","v6.18.45","v7.2-rc1","v7.2-rc5","v6.18.44","v7.2-rc7","v7.2-rc2","v7.2-rc6","v7.2-rc3","v6.18.43","v6.18.42","v7.2-rc4","v6.18.41","v6.18.40","v6.18.39","v6.18.38","v6.18.37","v6.18.36","v7.1","v7.1-rc1","v6.18.35","v7.1-rc7","v7.1-rc6","v7.1-rc4","v7.1-rc3","v6.18.34","v7.1-rc2","v7.1-rc5","v6.18.33","v6.18.32","v7.0","v6.18.31","v6.18.30","v6.18.29","v6.18.28","v6.18.27","v6.18.26","v7.0-rc1","v6.18.25","v6.18.24","v6.18.23","v6.18.22","v7.0-rc5","v7.0-rc6","v6.18.21","v7.0-rc7","v7.0-rc3","v7.0-rc4","v6.19-rc2","v6.18.20","v7.0-rc2","v6.19","v6.18.19","v6.18.18","v6.18.17","v6.18.16","v6.18.15","v6.18.14","v6.18.13","v6.18.12","v6.18.11","v6.18.10","v6.18.9","v6.19-rc8","v6.19-rc1","v6.19-rc6","v6.18.8","v6.19-rc7","v6.19-rc5","v6.19-rc4","v6.18.7","v6.19-rc3","v6.18.6","v6.18.5","v6.18.4","v6.18.3","v6.18.2","v6.18.1","v6.18","v6.18-rc1","v6.18-rc7","v6.18-rc3","v6.18-rc5","v6.18-rc6","v6.18-rc2","v6.18-rc4","v6.17","v6.17-rc7","v6.17-rc1","v6.17-rc2","v6.17-rc6","v6.17-rc4","v6.17-rc5","v6.17-rc3","v6.16","v6.16-rc6","v6.16-rc1","v6.16-rc4","v6.16-rc2","v6.16-rc5","v6.16-rc7","v6.16-rc3","v6.14-rc3","v6.15","v6.15-rc1","v6.15-rc6","v6.15-rc3","v6.15-rc2","v6.15-rc7","v6.15-rc4","v6.15-rc5","v6.14","v6.14-rc1","v6.14-rc7","v6.14-rc6","v6.14-rc4","v6.14-rc5","v6.14-rc2","v6.13","v6.13-rc1","v6.13-rc6","v6.13-rc7","v6.13-rc2","v6.13-rc5","v6.13-rc3","v6.12-rc1","v6.13-rc4","v6.12","v6.12-rc7","v6.12-rc3","v6.12-rc4","v6.12-rc6","v6.12-rc5","v6.12-rc2","v6.11-rc1","v6.11-rc5","v6.11","v6.11-rc7","v6.10-rc1","v6.11-rc6","v6.11-rc3","v6.11-rc4","v6.11-rc2","v6.10","v6.10-rc6","v6.10-rc7","v6.10-rc3","v6.9-rc1","v6.10-rc5","v6.10-rc2","v6.10-rc4","v6.9","v6.9-rc6","v6.9-rc7","v6.9-rc5","v6.9-rc3","v6.9-rc2","v6.8","v6.9-rc4","v6.8-rc1","v6.7-rc1","v6.8-rc7","v6.8-rc6","v6.8-rc5","v6.8-rc4","v6.8-rc3","v6.8-rc2","v6.7","v6.7-rc3","v6.7-rc8","v6.7-rc7","v6.7-rc6","v6.7-rc2","v6.7-rc4","v6.7-rc5","v6.6","v6.6-rc1","v6.6-rc5","v6.6-rc3","v6.6-rc7","v6.6-rc6","v6.6-rc4","v6.6-rc2","v6.5","v6.5-rc1","v6.5-rc2","v6.5-rc7","v6.5-rc4","v6.5-rc3","v6.5-rc6","v6.5-rc5","v6.4","v6.4-rc7","v6.4-rc1","v6.4-rc6","v6.4-rc5","v6.4-rc3","v6.4-rc4","v6.4-rc2","v6.3","v6.3-rc1","v6.3-rc7","v6.3-rc2","v6.3-rc3","v6.3-rc5","v6.3-rc6","v6.3-rc4","v6.2-rc6","v6.2-rc1","v6.2","v6.2-rc2","v6.2-rc8","v6.2-rc5","v6.2-rc4","v6.2-rc7","v6.2-rc3","v6.1-rc1","v6.1","v6.1-rc8","v6.1-rc3","v6.1-rc6","v6.1-rc7","v6.1-rc4","v6.1-rc2","v6.1-rc5","v6.0-rc1","v6.0","v6.0-rc7","v6.0-rc3","v6.0-rc2","v6.0-rc6","v6.0-rc4","v6.0-rc5","v5.19","v5.19-rc1","v5.19-rc5","v5.19-rc8","v5.19-rc6","v5.18","v5.19-rc2","v5.19-rc7","v5.19-rc3","v5.19-rc4","v5.18-rc1","v5.18-rc7","v5.18-rc2","v5.18-rc5","v5.17","v5.18-rc4","v5.18-rc3","v5.18-rc6","v5.17-rc6","v5.17-rc4","v5.17-rc8","v5.17-rc7","v5.17-rc1","v5.17-rc3","v5.17-rc2","v5.17-rc5","v5.16","v5.16-rc1","v5.16-rc8","v5.16-rc5","v5.16-rc6","v5.16-rc7","v5.16-rc3","v5.16-rc2","v5.16-rc4","v5.15","v5.15-rc2","v5.15-rc1","v5.15-rc4","v5.15-rc7","v5.15-rc3","v5.15-rc5","v5.15-rc6","v5.14","v5.14-rc3","v5.14-rc1","v5.14-rc2","v5.14-rc7","v5.14-rc6","v5.13-rc1","v5.14-rc5","v5.14-rc4","v5.13","v5.13-rc6","v5.13-rc7","v5.13-rc3","v5.13-rc2","v5.13-rc4","v5.13-rc5","v5.12","v5.12-rc2","v5.12-rc1-dontuse","v5.12-rc1","v5.12-rc8","v5.12-rc3","v5.12-rc7","v5.12-rc5","v5.12-rc6","v5.12-rc4","v5.10","v5.11","v5.11-rc3","v5.11-rc7","v5.11-rc6","v5.11-rc5","v5.11-rc1","v5.11-rc4","v5.11-rc2","v5.10-rc1","v5.10-rc7","v5.10-rc4","v5.10-rc3","v5.10-rc6","v5.9","v5.10-rc2","v5.10-rc5","v5.9-rc1","v5.9-rc7","v5.9-rc8","v5.9-rc6","v5.9-rc4","v5.9-rc5","v5.9-rc3","v5.9-rc2","v5.8","v5.7","v5.8-rc2","v5.8-rc1","v5.8-rc7","v5.8-rc5","v5.8-rc3","v5.8-rc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