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 numaces to le16") split struct smbacl'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 buildsecdesc(), 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 "ndrpullsecurity_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/20233ed8-a6c6-4097-aafa-dd545ed24428
{
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46139.json",
"cna_assigner": "Linux"
}