CVE-2026-52906 Details
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.
A vulnerability in the Linux kernel's 9P file system implementation can lead to improper handling of access mode flags, causing issues with user permissions. When the 9P2000.L protocol is used, the default access flag allows for certain operations to be performed by the root user. However, due to a flaw in how access flags are applied, both the default and user-specified access flags can end up set simultaneously. This conflict prevents access mode checks from functioning correctly, causing the system to revert to a default user ID that lacks the necessary privileges. As a result, the root user may be unable to perform critical operations such as changing file ownership or executing other privileged tasks.
Users can upgrade to the latest version of the Linux kernel where this vulnerability has been addressed. Instructions for downloading the patched kernel are available on the official Linux kernel website.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
No SSVC data is available for this CVE.
References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://git.kernel.org/stable/c/b8f037e87a083291190204b959cda417aaf01058 | kernel.org | Patch |
| https://git.kernel.org/stable/c/da2346a48a5a1fed86c3fe3d73c0b60e7b3027c9 | kernel.org | Patch |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| NVD-CWE-noinfo | Insufficient Information to Classify Weakness | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| linux linux kernel | >= 6.19, < 7.0.4 |
CPE
Remediation
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Change History
5 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 23, 2026 | CVE Translated | [email protected] |
| Jul 8, 2026 | Initial Analysis | [email protected] |
| Jun 17, 2026 | CVE Modified | kernel.org |
| Jun 14, 2026 | CVE Modified | kernel.org |
| Jun 9, 2026 | New CVE Received | kernel.org |