CVE-2026-46139

/// Technical description

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

smb: client: use kzalloc to zero-initialize security descriptor buffer

Commit 62e7dd0a39c2d ("smb: common: change the data type of num_aces

to le16") split struct smb_acl's __le32 num_aces field into __le16

num_aces and __le16 reserved. The reserved field corresponds to Sbz2

in the MS-DTYP ACL wire format, which must be zero [1].

When building an ACL descriptor in build_sec_desc(), we are using a

kmalloc()'ed descriptor buffer and writing the fields explicitly using

le16() writes now. This never writes to the 2 byte reserved field,

leaving it as uninitialized heap data.

When the reserved field happens to contain non-zero slab garbage,

Samba rejects the security descriptor with "ndr_pull_security_descriptor

failed: Range Error", causing chmod to fail with EINVAL.

Change kmalloc() to kzalloc() to ensure the entire buffer is

zero-initialized.

[1] https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-dtyp

/// 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