CVE-2025-37785 (GCVE-0-2025-37785)
Vulnerability from cvelistv5
Published
2025-04-18 07:01
Modified
2026-08-05 11:57
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ext4: fix OOB read when checking dotdot dir Mounting a corrupted filesystem with directory which contains '.' dir entry with rec_len == block size results in out-of-bounds read (later on, when the corrupted directory is removed). ext4_empty_dir() assumes every ext4 directory contains at least '.' and '..' as directory entries in the first data block. It first loads the '.' dir entry, performs sanity checks by calling ext4_check_dir_entry() and then uses its rec_len member to compute the location of '..' dir entry (in ext4_next_entry). It assumes the '..' dir entry fits into the same data block. If the rec_len of '.' is precisely one block (4KB), it slips through the sanity checks (it is considered the last directory entry in the data block) and leaves "struct ext4_dir_entry_2 *de" point exactly past the memory slot allocated to the data block. The following call to ext4_check_dir_entry() on new value of de then dereferences this pointer which results in out-of-bounds mem access. Fix this by extending __ext4_check_dir_entry() to check for '.' dir entries that reach the end of data block. Make sure to ignore the phony dir entries for checksum (by checking name_len for non-zero). Note: This is reported by KASAN as use-after-free in case another structure was recently freed from the slot past the bound, but it is really an OOB read. This issue was found by syzkaller tool. Call Trace: [ 38.594108] BUG: KASAN: slab-use-after-free in __ext4_check_dir_entry+0x67e/0x710 [ 38.594649] Read of size 2 at addr ffff88802b41a004 by task syz-executor/5375 [ 38.595158] [ 38.595288] CPU: 0 UID: 0 PID: 5375 Comm: syz-executor Not tainted 6.14.0-rc7 #1 [ 38.595298] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [ 38.595304] Call Trace: [ 38.595308] <TASK> [ 38.595311] dump_stack_lvl+0xa7/0xd0 [ 38.595325] print_address_description.constprop.0+0x2c/0x3f0 [ 38.595339] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595349] print_report+0xaa/0x250 [ 38.595359] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595368] ? kasan_addr_to_slab+0x9/0x90 [ 38.595378] kasan_report+0xab/0xe0 [ 38.595389] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595400] __ext4_check_dir_entry+0x67e/0x710 [ 38.595410] ext4_empty_dir+0x465/0x990 [ 38.595421] ? __pfx_ext4_empty_dir+0x10/0x10 [ 38.595432] ext4_rmdir.part.0+0x29a/0xd10 [ 38.595441] ? __dquot_initialize+0x2a7/0xbf0 [ 38.595455] ? __pfx_ext4_rmdir.part.0+0x10/0x10 [ 38.595464] ? __pfx___dquot_initialize+0x10/0x10 [ 38.595478] ? down_write+0xdb/0x140 [ 38.595487] ? __pfx_down_write+0x10/0x10 [ 38.595497] ext4_rmdir+0xee/0x140 [ 38.595506] vfs_rmdir+0x209/0x670 [ 38.595517] ? lookup_one_qstr_excl+0x3b/0x190 [ 38.595529] do_rmdir+0x363/0x3c0 [ 38.595537] ? __pfx_do_rmdir+0x10/0x10 [ 38.595544] ? strncpy_from_user+0x1ff/0x2e0 [ 38.595561] __x64_sys_unlinkat+0xf0/0x130 [ 38.595570] do_syscall_64+0x5b/0x180 [ 38.595583] entry_SYSCALL_64_after_hwframe+0x76/0x7e
References
Impacted products
Vendor Product Version
Linux Linux Version: ac27a0ec112a089f1a5102bc8dffc79c8c815571
Version: ac27a0ec112a089f1a5102bc8dffc79c8c815571
Version: ac27a0ec112a089f1a5102bc8dffc79c8c815571
Version: ac27a0ec112a089f1a5102bc8dffc79c8c815571
Version: ac27a0ec112a089f1a5102bc8dffc79c8c815571
Version: ac27a0ec112a089f1a5102bc8dffc79c8c815571
Version: ac27a0ec112a089f1a5102bc8dffc79c8c815571
Version: ac27a0ec112a089f1a5102bc8dffc79c8c815571
Version: ac27a0ec112a089f1a5102bc8dffc79c8c815571
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix OOB read when checking dotdot dir\n\nMounting a corrupted filesystem with directory which contains \u0027.\u0027 dir\nentry with rec_len == block size results in out-of-bounds read (later\non, when the corrupted directory is removed).\n\next4_empty_dir() assumes every ext4 directory contains at least \u0027.\u0027\nand \u0027..\u0027 as directory entries in the first data block. It first loads\nthe \u0027.\u0027 dir entry, performs sanity checks by calling ext4_check_dir_entry()\nand then uses its rec_len member to compute the location of \u0027..\u0027 dir\nentry (in ext4_next_entry). It assumes the \u0027..\u0027 dir entry fits into the\nsame data block.\n\nIf the rec_len of \u0027.\u0027 is precisely one block (4KB), it slips through the\nsanity checks (it is considered the last directory entry in the data\nblock) and leaves \"struct ext4_dir_entry_2 *de\" point exactly past the\nmemory slot allocated to the data block. The following call to\next4_check_dir_entry() on new value of de then dereferences this pointer\nwhich results in out-of-bounds mem access.\n\nFix this by extending __ext4_check_dir_entry() to check for \u0027.\u0027 dir\nentries that reach the end of data block. Make sure to ignore the phony\ndir entries for checksum (by checking name_len for non-zero).\n\nNote: This is reported by KASAN as use-after-free in case another\nstructure was recently freed from the slot past the bound, but it is\nreally an OOB read.\n\nThis issue was found by syzkaller tool.\n\nCall Trace:\n[   38.594108] BUG: KASAN: slab-use-after-free in __ext4_check_dir_entry+0x67e/0x710\n[   38.594649] Read of size 2 at addr ffff88802b41a004 by task syz-executor/5375\n[   38.595158]\n[   38.595288] CPU: 0 UID: 0 PID: 5375 Comm: syz-executor Not tainted 6.14.0-rc7 #1\n[   38.595298] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014\n[   38.595304] Call Trace:\n[   38.595308]  \u003cTASK\u003e\n[   38.595311]  dump_stack_lvl+0xa7/0xd0\n[   38.595325]  print_address_description.constprop.0+0x2c/0x3f0\n[   38.595339]  ? __ext4_check_dir_entry+0x67e/0x710\n[   38.595349]  print_report+0xaa/0x250\n[   38.595359]  ? __ext4_check_dir_entry+0x67e/0x710\n[   38.595368]  ? kasan_addr_to_slab+0x9/0x90\n[   38.595378]  kasan_report+0xab/0xe0\n[   38.595389]  ? __ext4_check_dir_entry+0x67e/0x710\n[   38.595400]  __ext4_check_dir_entry+0x67e/0x710\n[   38.595410]  ext4_empty_dir+0x465/0x990\n[   38.595421]  ? __pfx_ext4_empty_dir+0x10/0x10\n[   38.595432]  ext4_rmdir.part.0+0x29a/0xd10\n[   38.595441]  ? __dquot_initialize+0x2a7/0xbf0\n[   38.595455]  ? __pfx_ext4_rmdir.part.0+0x10/0x10\n[   38.595464]  ? __pfx___dquot_initialize+0x10/0x10\n[   38.595478]  ? down_write+0xdb/0x140\n[   38.595487]  ? __pfx_down_write+0x10/0x10\n[   38.595497]  ext4_rmdir+0xee/0x140\n[   38.595506]  vfs_rmdir+0x209/0x670\n[   38.595517]  ? lookup_one_qstr_excl+0x3b/0x190\n[   38.595529]  do_rmdir+0x363/0x3c0\n[   38.595537]  ? __pfx_do_rmdir+0x10/0x10\n[   38.595544]  ? strncpy_from_user+0x1ff/0x2e0\n[   38.595561]  __x64_sys_unlinkat+0xf0/0x130\n[   38.595570]  do_syscall_64+0x5b/0x180\n[   38.595583]  entry_SYSCALL_64_after_hwframe+0x76/0x7e"
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      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Triggering requires a crafted ext4 image to be mounted locally and then an `unlinkat(AT_REMOVEDIR)`/rename syscall against the corrupted directory; there is no network-facing path to `ext4_empty_dir()`. Local attack vector scores higher than physical and correctly models USB/auto-mount and loop-mount delivery.\nAC:L - The condition is fully deterministic and entirely attacker-authored \u2014 setting the `.` entry\u0027s `rec_len` to exactly the block size in the image reliably slips past every sanity check in `__ext4_check_dir_entry()` and lands `de` past the block on every attempt. No race, timing, or uncontrolled memory-layout requirement.\nPR:L - Once the image is mounted (via udisks2/GNOME auto-mount of removable media on desktops and kiosks, or an fstab `user` entry), any unprivileged local user with ordinary access to the mount can invoke `rmdir` and reach `ext4_empty_dir()`; no capability check gates the path.\nUI:N - In the auto-mount scenario the attacker performs both steps themselves \u2014 inserting the media triggers the mount automatically and the same attacker issues the `rmdir` \u2014 so no action by a separate user is required.\nS:U - The out-of-bounds access, the disclosure, and the panic all occur within the kernel\u0027s own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The read reaches into the adjacent slab object/page and its contents are exfiltrated to userspace-visible dmesg through `ext4_error_inode()`, which prints the out-of-bounds `inode` and `rec_len` fields verbatim. The operation is cheaply repeatable and the neighbouring slot can be heap-groomed, making it a practical kernel heap/pointer disclosure primitive rather than a bounded one-shot leak.\nI:H - Data read out of bounds directly controls subsequent logic \u2014 if the adjacent heap bytes decode as a valid `..` entry, `ext4_empty_dir()` wrongly reports the directory empty and `rmdir`/`rename` proceeds to unlink a non-empty directory, and the OOB `rec_len` drives the following offset walk. KASAN classifies the access as a use-after-free on the neighbouring freed object, so attacker-groomed heap state translates into corrupted filesystem-metadata operations.\nA:H - The error path is reached with the attacker-controlled superblock, and `s_errors = EXT4_ERRORS_PANIC` (`fs/ext4/super.c:4364`) makes `ext4_error_inode()` call `panic()` at `super.c:735`, giving a guaranteed kernel panic. Independently, the read past the block can fault on an unmapped or poisoned page, and on debug/KASAN kernels it is an immediate BUG."
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        "dateUpdated": "2026-08-05T11:57:31.764Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        {
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      "title": "ext4: fix OOB read when checking dotdot dir",
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-37785",
    "datePublished": "2025-04-18T07:01:27.393Z",
    "dateReserved": "2025-04-16T04:51:23.940Z",
    "dateUpdated": "2026-08-05T11:57:31.764Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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  • Patched: This vulnerability was successfully patched by the user reporting the sighting.
  • Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
  • Not confirmed: The user expresses doubt about the veracity of the vulnerability.
  • Not patched: This vulnerability was not successfully patched by the user reporting the sighting.