# CVE-2026-52906: linux: In the Linux kernel, the following vulnerability has been resolved:  9p: fix access mode flags being ORed instead of...

CVE-2026-52906 is fixed in linux on 1 platform by DEBIAN-CVE-2026-52906 (version 7.0.4-1), released June 24, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-52906
- Priority: High
- CVSS: 7.7 (high)
- EPSS: 0.0012
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 9, 2026

## Description

In the Linux kernel, the following vulnerability has been resolved:  9p: fix access mode flags being ORed instead of replaced  Since commit 1f3e4142c0eb ("9p: convert to the new mount API"), v9fs_apply_options() applies parsed mount flags with |= onto flags already set by v9fs_session_init(). For 9P2000.L, session_init sets V9FS_ACCESS_CLIENT as the default, so when the user mounts with "access=user", both bits end up set. Access mode checks compare against exact values, so having both bits set matches neither mode.  This causes v9fs_fid_lookup() to fall through to the default switch case, using INVALID_UID (nobody/65534) instead of current_fsuid() for all fid lookups. Root is then unable to chown or perform other privileged operations.  Fix by clearing the access mask before applying the user's choice.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 14 | 7.0.4-1 | [DEBIAN-CVE-2026-52906](https://patchblox.com/security/data/fix/linux/debian-cve-2026-52906.md) | Jun 24, 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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