← CVE Intelligence

CVE-2026-98979

namespace: refuse an automount below a mount that is in no namespace PUBLISHED

Description (CNA)

In the Linux kernel, the following vulnerability has been resolved: namespace: refuse an automount below a mount that is in no namespace It's possible to add autmounts even when the parent mount isn't in the mount namespace of the caller. The only requirement we have is that the parent mount namespace must not be NULL, i.e., unmounted. Problem is that clone_private_mount() has MNT_NS_INTERNAL which makes that trivially true. So that passes the test and attach_recursive_mnt() accepts that as a mount point and funny enough, count_mounts() dereferences MNT_NS_INTERNAL. The problem is it is an error pointer... So we can reach this in userspace via fanotify. A filesystem mark on the lower filesystem of an overlay reports paths on the layer clone and reading the event hands out a descriptor on it. For example with debugfs as the lower layer it goes kaboom: openat(evfd, "tracing", O_DIRECTORY) Oops: general protection fault KASAN: null-ptr-deref in range [0x1d0-0x1d7] RIP: 0010:count_mounts+0x35/0x200 attach_recursive_mnt finish_automount And since that sleeping beauty happens under namespace_sem held for writing every mount operation on the system blocks from then on. Congrats. Use is_mounted() instead which rejects unmounted and internal mounts alike. The open fails with EINVAL just as it did before clone_private_mount() used MNT_NS_INTERNAL.

Affected (CNA)

Vendor / productVersions
Linux / Linuxaffected df820f8de4e481222b17f9bcee7b909ae8167529 before 95fb7c259b86f5521f04973040ad492f2bef6f82; affected df820f8de4e481222b17f9bcee7b909ae8167529 before 35f2013f83ef16f9f0331c4c3a8e8d161580d574; affected df820f8de4e481222b17f9bcee7b909ae8167529 before 494c57572d2d5bc2839553ed41aabe92ed0f587c; affected df820f8de4e481222b17f9bcee7b909ae8167529 before 776e20e4fdc23c23687b511ffdc80047878049d3; affected df820f8de4e481222b17f9bcee7b909ae8167529 before ba985ce08471c555af2a2fbe217c1bc2e72a6d8c
Linux / Linuxaffected 5.8; unaffected 0 before 5.8; unaffected 6.6.160 through 6.6.*; unaffected 6.12.113 through 6.12.*; unaffected 6.18.57 through 6.18.*; unaffected 7.2.11 through 7.2.*; unaffected 7.3 through *

CWE

No CWE identifiers supplied.

References