CVE-2026-97559

/// Technical description

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

smb: client: fail DACL rewrite when the new DACL exceeds 64K

replace_sids_and_copy_aces() and set_chmod_dacl() accumulate the size of

the DACL they build in a u16. That accumulator can wrap.

validate_dacl() caps num_aces at (dacl_size - sizeof(struct smb_acl)) /

20, i.e. 3276 for a maximally sized DACL, while each rewritten ACE can

grow to sizeof(struct smb_ace) (76 bytes) once its SID is replaced with

one carrying SID_MAX_SUB_AUTHORITIES sub-authorities. The worst case is

therefore sizeof(struct smb_acl) + 3276 * 76 = 248984 bytes, far beyond

what a u16 can hold. A wraparound is reached with 863 ACEs.

After the wraparound, ndacl_ptr->size becomes meaningless and the offset

will point anywhere in the ACE array. As a result, we will see

corruption of the DACL, which then gets sent to the server. This is not

an out-of-bounds write as the allocation now covers the worst-case

expansion, so writes will always go into th

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References