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CVE-2026-97555: Linux

Severity

8.8 (HIGH)

Vendor

LINUX

Affected versions

bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 through before fb736ab4fb8c4fdb8b2f9ccd3a62e03d11549ca1; bc3e9dd9d104ca1b75644e

Patch status

Patched

Published

2026-09-25T11:17:05.963

Modified

2026-09-25T15:17:58.803

Why it matters

High-severity vulnerability requiring prioritized review.

Recommended admin actions

• Review and patch based on exposure, asset criticality, and business impact.

Technical summary

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)

View the official NVD record for CVE-2026-97555

CVE data is sourced from NVD/CNA records and optional enrichment. Validate against the vendor advisory before taking production action.