From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-72034: fhandle: reject detached mounts in capable_wrt_mount()
Date: Sat, 15 Aug 2026 15:01:53 +0900 [thread overview]
Message-ID: <2026081512-CVE-2026-72034-a89c@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
fhandle: reject detached mounts in capable_wrt_mount()
The recent fhandle RCU fix moved the mount namespace capability check
into capable_wrt_mount(), so a non-NULL mnt_namespace survives the
ns_capable() dereference. The helper still assumes the later
READ_ONCE(mount->mnt_ns) must be non-NULL because may_decode_fh()
checked is_mounted() first.
That assumption is not stable. A detached mount from
open_tree(..., OPEN_TREE_CLONE) can be dissolved on fput while
open_by_handle_at() is between those checks, and umount_tree() can
clear mount->mnt_ns. If the helper observes NULL, it dereferences
mnt_ns->user_ns and panics.
Return false when the RCU read observes a detached mount. This keeps
the relaxed permission path conservative: a mount no longer attached
to a namespace cannot authorize open_by_handle_at() access.
The Linux kernel CVE team has assigned CVE-2026-72034 to this issue.
Affected and fixed versions
===========================
Issue introduced in 6.11 with commit 620c266f394932e5decc4b34683a75dfc59dc2f4 and fixed in 6.12.97 with commit 15104234c267ebe04b9f9a73e5c2179cc265ff60
Issue introduced in 6.11 with commit 620c266f394932e5decc4b34683a75dfc59dc2f4 and fixed in 6.18.40 with commit 6c52226072a3c61337b1eec1799bb987748884fa
Issue introduced in 6.11 with commit 620c266f394932e5decc4b34683a75dfc59dc2f4 and fixed in 7.1.5 with commit 6ee183d89261bf1d1cf9f06d80a40dab8f36ee55
Issue introduced in 6.11 with commit 620c266f394932e5decc4b34683a75dfc59dc2f4 and fixed in 7.2-rc2 with commit 6c732471740bc2ac9b0946134f9f551dc75f4369
Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.
Unaffected versions might change over time as fixes are backported to
older supported kernel versions. The official CVE entry at
https://cve.org/CVERecord/?id=CVE-2026-72034
will be updated if fixes are backported, please check that for the most
up to date information about this issue.
Affected files
==============
The file(s) affected by this issue are:
fs/fhandle.c
Mitigation
==========
The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes. Individual
changes are never tested alone, but rather are part of a larger kernel
release. Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all. If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
https://git.kernel.org/stable/c/15104234c267ebe04b9f9a73e5c2179cc265ff60
https://git.kernel.org/stable/c/6c52226072a3c61337b1eec1799bb987748884fa
https://git.kernel.org/stable/c/6ee183d89261bf1d1cf9f06d80a40dab8f36ee55
https://git.kernel.org/stable/c/6c732471740bc2ac9b0946134f9f551dc75f4369
reply other threads:[~2026-08-15 6:08 UTC|newest]
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