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CVE-2026-31706: Linux

8.8

CVSS 3.1

Няма данни

Вероятност да бъде експлоатирана в следващите 30 дни (EPSS)

Няма потвърждение

Атакува се

Няма данни

Време до експлоатация

Атакува се по мрежата, без особени условия, с обикновен потребителски вход и без действие от потребителя.

    Описание

    Оригинално описание

    In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate num_aces and harden ACE walk in smb_inherit_dacl() smb_inherit_dacl() trusts the on-disk num_aces value from the parent directory's DACL xattr and uses it to size a heap allocation: aces_base = kmalloc(sizeof(struct smb_ace) * num_aces * 2, ...); num_aces is a u16 read from le16_to_cpu(parent_pdacl->num_aces) without checking that it is consistent with the declared pdacl_size. An authenticated client whose parent directory's security.NTACL is tampered (e.g. via offline xattr corruption or a concurrent path that bypasses parse_dacl()) can present num_aces = 65535 with minimal actual ACE data. This causes a ~8 MB allocation (not kzalloc, so uninitialized) that the subsequent loop only partially populates, and may also overflow the three-way size_t multiply on 32-bit kernels. Additionally, the ACE walk loop uses the weaker offsetof(struct smb_ace, access_req) minimum size check rather than the minimum valid on-wire ACE size, and does not reject ACEs whose declared size is below the minimum. Reproduced on UML + KASAN + LOCKDEP against the real ksmbd code path. A legitimate mount.cifs client creates a parent directory over SMB (ksmbd writes a valid security.NTACL xattr), then the NTACL blob on the backing filesystem is rewritten to set num_aces = 0xFFFF while keeping the posix_acl_hash bytes intact so ksmbd_vfs_get_sd_xattr()'s hash check still passes. A subsequent SMB2 CREATE of a child under that parent drives smb2_open() into smb_inherit_dacl() (share has "vfs objects = acl_xattr" set), which fails the page allocator: WARNING: mm/page_alloc.c:5226 at __alloc_frozen_pages_noprof+0x46c/0x9c0 Workqueue: ksmbd-io handle_ksmbd_work __alloc_frozen_pages_noprof+0x46c/0x9c0 ___kmalloc_large_node+0x68/0x130 __kmalloc_large_node_noprof+0x24/0x70 __kmalloc_noprof+0x4c9/0x690 smb_inherit_dacl+0x394/0x2430 smb2_open+0x595d/0xabe0 handle_ksmbd_work+0x3d3/0x1140 W

    Засегнати продукти

    • Linux Linux: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 преди 4d37830c2c834987de329d58fb9a319067400361; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 преди ad7d18df7423c522ed9dc7e33bd5d54c66b1bc37; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 преди 063a7409b0de46d7c770b65bb0338e6fdb3b1f0a; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 преди 3e5360b422dd741cb315654a191fa73869a37414; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 преди 59c32abaaec9cdd6164811c7e864e72f7554b82d; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 преди 3e4e2ea2a781018ed5d75f969e3e5606beb66e48
    • Linux Linux: 5.15; преди 5.15; 6.1.191 до 6.1.*; 6.6.160 до 6.6.*; 6.12.84 до 6.12.*; 6.18.25 до 6.18.*; 7.0.2 до 7.0.*; от 7.1 нататък

    История

    • 1 май 2026 Публикувано

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    Първоизточници

    CVE-2026-31706: Linux | freedomonline.bg