CVE-2026-97555

Status: UPDATED  |  Advisory ID: CVE-2026-97555

Key Details

Affected Products, Subsystems & Sectors

What to Know

In the Linux kernel, the following vulnerability has been resolved:

smb: client: fix heap overflow in DACL owner/group rewrite

When id_mode_to_cifs_acl rewrites an existing DACL, it allocates a

buffer sized according to the on-disk DACL length reported by

dacl_ptr->size. However, replace_sids_and_copy_aces may rewrite each

ACE with a new owner/group SID obtained from the cifs.idmap upcall.

Those SIDs can have up to SID_MAX_SUB_AUTHORITIES (15) sub-authorities,

making each ACE up to 76 bytes (sizeof(struct smb_ace)).

If the original DACL contains short SIDs (e.g., 1 sub-authority) while

the replacement SIDs are long, the rewritten ACEs overflow the

allocation.

Fix this by always budgeting for worst-case SID expansion: allocate

sizeof(struct smb_acl) plus num_aces * sizeof(struct smb_ace), which

covers the smb_acl header and room for every ACE at maximum SID size.

This replaces the previous split logic that used dacl_ptr->size for

cifsacl mounts but num_aces * sizeof(struct smb_ace) for mode_from_sid

mounts: both paths can trigger the same rewrite and need the same

headroom.

KASAN reports this as:

BUG: KASAN: slab-out-of-bounds in build_sec_desc+0x1e8a/0x2680 [cifs]

Write of size 4 at addr ffff8881a5e25374 by task chown/5298

...

The buggy address is located 0 bytes to the right of

allocated 884-byte region [ffff8881a5e25000, ffff8881a5e25374) (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References