CVE-2026-52906: high-severity vulnerability in Linux
9p: fix access mode flags being ORed instead of replaced
Published · Updated
21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.7epss 0.2%
exploitation probability
0.2%top 93% of all CVEs
observed exploitation
nono source reports it
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.
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Affected products
Linux · LinuxRelated CVEs — Linux
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