# CVE-2026-31432: ksmbd: fix OOB write in QUERY_INFO for compound requests

CVE-2026-31432 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-31432, released May 15, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-31432
- Priority: High
- CVSS: 8.8 (Important)
- EPSS: 0.0055
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 22, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-31432

## Description

In the Linux kernel, the following vulnerability has been resolved:  ksmbd: fix OOB write in QUERY_INFO for compound requests  When a compound request such as READ + QUERY_INFO(Security) is received, and the first command (READ) consumes most of the response buffer, ksmbd could write beyond the allocated buffer while building a security descriptor.  The root cause was that smb2_get_info_sec() checked buffer space using ppntsd_size from xattr, while build_sec_desc() often synthesized a significantly larger descriptor from POSIX ACLs.  This patch introduces smb_acl_sec_desc_scratch_len() to accurately compute the final descriptor size beforehand, performs proper buffer checking with smb2_calc_max_out_buf_len(), and uses exact-sized allocation + iov pinning.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.12.85-1 | [DEBIAN-CVE-2026-31432](https://patchblox.com/security/data/fix/linux/debian-cve-2026-31432.md) | May 15, 2026 |
| Linux | linux Debian 14 | 6.19.12-1 | [DEBIAN-CVE-2026-31432](https://patchblox.com/security/data/fix/linux/debian-cve-2026-31432.md) | May 15, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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