# CVE-2026-64391: ksmbd: use opener credentials for ADS I/O

CVE-2026-64391 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-64391, released July 26, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-64391
- Priority: High
- CVSS: 9.8 (Important)
- EPSS: 0.0049
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 25, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-64391

## Description

In the Linux kernel, the following vulnerability has been resolved:  ksmbd: use opener credentials for ADS I/O  Alternate data streams are stored as xattrs. Unlike regular file I/O, their read and write paths therefore call VFS xattr helpers which recheck inode permissions and LSM policy using the current task credentials.  Run ADS I/O with the credentials captured when the SMB handle was opened.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.12.96-1 | [DEBIAN-CVE-2026-64391](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64391.md) | Jul 26, 2026 |
| Linux | linux Debian 14 | 7.1.4-1 | [DEBIAN-CVE-2026-64391](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64391.md) | Jul 26, 2026 |
| Linux | linux-6.12 Debian 12.15 (bookworm) | 6.12.100-1~deb12u1 | [DEBIAN-CVE-2026-64391](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64391.md) | Jul 26, 2026 |

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Data as of 2026-11-08T19:12:23Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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