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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-98979
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-23 13:17:19 UTC
Updated2026-10-23 13:17:19 UTC
DescriptionIn 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.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected df820f8de4e481222b17f9bcee7b909ae8167529 95fb7c259b86f5521f04973040ad492f2bef6f82 git Not specified
CNA Linux Linux affected df820f8de4e481222b17f9bcee7b909ae8167529 35f2013f83ef16f9f0331c4c3a8e8d161580d574 git Not specified
CNA Linux Linux affected df820f8de4e481222b17f9bcee7b909ae8167529 494c57572d2d5bc2839553ed41aabe92ed0f587c git Not specified
CNA Linux Linux affected df820f8de4e481222b17f9bcee7b909ae8167529 776e20e4fdc23c23687b511ffdc80047878049d3 git Not specified
CNA Linux Linux affected df820f8de4e481222b17f9bcee7b909ae8167529 ba985ce08471c555af2a2fbe217c1bc2e72a6d8c git Not specified
CNA Linux Linux affected 5.8 Not specified
CNA Linux Linux unaffected 5.8 semver Not specified
CNA Linux Linux unaffected 6.6.160 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.113 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.57 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.11 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/776e20e4fdc23c23687b511ffdc80047878049d3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ba985ce08471c555af2a2fbe217c1bc2e72a6d8c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/494c57572d2d5bc2839553ed41aabe92ed0f587c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/35f2013f83ef16f9f0331c4c3a8e8d161580d574 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/95fb7c259b86f5521f04973040ad492f2bef6f82 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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