# CVE-2026-31705: ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment

CVE-2026-31705 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-31705, released May 15, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2026-31705
- Priority: Urgent
- CVSS: 9.8 (Critical)
- EPSS: 0.0040
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 1, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-31705

## Description

In the Linux kernel, the following vulnerability has been resolved:  ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment  smb2_get_ea() applies 4-byte alignment padding via memset() after writing each EA entry. The bounds check on buf_free_len is performed before the value memcpy, but the alignment memset fires unconditionally afterward with no check on remaining space.  When the EA value exactly fills the remaining buffer (buf_free_len == 0 after value subtraction), the alignment memset writes 1-3 NUL bytes past the buf_free_len boundary. In compound requests where the response buffer is shared across commands, the first command (e.g., READ) can consume most of the buffer, leaving a tight remainder for the QUERY_INFO EA response. The alignment memset then overwrites past the physical kvmalloc allocation into adjacent kernel heap memory.  Add a bounds check before the alignment memset to ensure buf_free_len can accommodate the padding bytes.  This is the same bug pattern fixed by commit beef2634f81f ("ksmbd: fix potencial OOB in get_file_all_info() for compound requests") and commit fda9522ed6af ("ksmbd: fix OOB write in QUERY_INFO for compound requests"), both of which added bounds checks before unconditional writes in QUERY_INFO response handlers.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.176-1 | [DEBIAN-CVE-2026-31705](https://patchblox.com/security/data/fix/linux/debian-cve-2026-31705.md) | May 15, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.85-1 | [DEBIAN-CVE-2026-31705](https://patchblox.com/security/data/fix/linux/debian-cve-2026-31705.md) | May 15, 2026 |
| Linux | linux Debian 14 | 7.0.3-1 | [DEBIAN-CVE-2026-31705](https://patchblox.com/security/data/fix/linux/debian-cve-2026-31705.md) | May 15, 2026 |

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Data as of 2026-11-09T01:18:40Z 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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