Description
fs/namespace.c in the Linux kernel before 4.0.2 processes MNT_DETACH umount2 system calls without verifying that the MNT_LOCKED flag is unset, which allows local users to bypass intended access restrictions and navigate to filesystem locations beneath a mount by calling umount2 within a user namespace.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | linux | 4.0.2-1 | — |
| Debian 13 | linux | 4.0.2-1 | — |
| Debian 12 | linux | 4.0.2-1 | — |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP1 | kernel-docs | 3.12.59-60.41.8 | SUSE-SU-2016:1696-1 |
| SLES 12 SP1 | kernel-syms | 3.12.59-60.41.1 | SUSE-SU-2016:1696-1 |
| SLES 12 SP1 | kernel-xen +3 | 3.12.59-60.41.2 | SUSE-SU-2016:1696-1 |
| SLES 12 | kernel-docs | 3.12.60-52.49.3 | SUSE-SU-2016:1690-1 |
| SLES 12 | kernel-ec2 | 3.12.59-60.41.2 | SUSE-SU-2016:1696-1, SUSE-SU-2016:1690-1 |
| SLES 12 | kernel-xen +4 | 3.12.60-52.49.1 | SUSE-SU-2016:1690-1 |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 12 SP1 | kernel-syms | 3.12.59-60.41.1 | SUSE-SU-2016:1696-1 |
| SLES for SAP 12 SP1 | kernel-xen +2 | 3.12.59-60.41.2 | SUSE-SU-2016:1696-1 |
| SLES for SAP 12 | kernel-xen +3 | 3.12.60-52.49.1 | SUSE-SU-2016:1690-1 |
| SLE Real Time 12 SP1 | kernel-rt +5 | 3.12.61-60.18.1 | SUSE-SU-2016:1937-1 |
| SLE Live Patching 12 | kgraft-patch-SLE12_Update_14 +1 | 1-2.1 | SUSE-SU-2016:1696-1, SUSE-SU-2016:1690-1 |
Advisories 3
- SUSE-SU-2016:1937-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2016:1696-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2016:1690-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · May 2, 2025
References
- SUSE-SU-2016:1690 vendor-advisory
- SUSE-SU-2016:1696 vendor-advisory
- https://github.com/torvalds/linux/commit/ce07d891a0891d3c0d0c2d73d577490486b809e1
- [oss-security] 20150417 USERNS allows circumventing MNT_LOCKED mailing-list
- http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ce07d891a0891d3c0d0c2d73d577490486b809e1
- https://bugzilla.redhat.com/show_bug.cgi?id=1226751
- [linux-kernel] 20141007 [PATCH] mnt: don't allow to detach the namespace root mailing-list
- [containers] 20150402 [PATCH review 0/19] Locked mount and loopback mount fixes mailing-list
- 74226 vdb-entry
- http://www.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.0.2
- SUSE-SU-2016:1937 vendor-advisory