CVE-2026-98985
Received
Received - Intake
Memory Corruption in Linux Kernel pivot_root
Vulnerability report for CVE-2026-98985, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-10-23
Last updated on: 2026-10-23
Assigner: kernel.org
Description
Description
In the Linux kernel, the following vulnerability has been resolved:
namespace: check the mounts before reading their parents in pivot_root()
path_pivot_root() reads the parents of new_root and of the caller's root
and checks whether they are shared before it checks that either mount is
in the caller's mount namespace. Only namespace_sem is held. That's fine
for a mount that is in the caller's mount namespace.
But new_root can be a file descriptor to a mount that has been unmounted
and that only the file descriptor keeps alive. If that mount stayed
attached to its parent when it was unmounted nothing pins the parent for
it. The final mntput() of the parent unhooks the children under
mount_lock alone and frees the parent afterwards:
pivot_root() close(fd), last ref on the parent
------------ ---------------------------------
ex_parent = new_mnt->mnt_parent
mntput_no_expire_slowpath()
__umount_mnt(new_mnt)
cleanup_mnt()
call_rcu()
IS_MNT_SHARED(ex_parent)
BUG: KASAN: slab-use-after-free in path_pivot_root+0xf1a/0x1840
Read of size 4 at addr ffff8881047382f8 by task pivot_widen/157
path_pivot_root+0xf1a/0x1840
__x64_sys_pivot_root+0x165/0x190
The same goes for the caller's root via chroot(). Both outcomes of the
check end in EINVAL so nothing but the read itself goes wrong. It's the
same thing commit bb4609405752 ("statmount: read the parent of an
unmounted mount under mount_lock") fixed for statmount().
Check that both mounts are in the caller's namespace before their
parents are read. Every path returns EINVAL either way.
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| Linux | Linux | e0c9c0afd2fc958ffa34b697972721d81df8a56f |
| Linux | Linux | e0c9c0afd2fc958ffa34b697972721d81df8a56f |
| Linux | Linux | e0c9c0afd2fc958ffa34b697972721d81df8a56f |
| Linux | Linux | e0c9c0afd2fc958ffa34b697972721d81df8a56f |
| Linux | Linux | e0c9c0afd2fc958ffa34b697972721d81df8a56f |
| Linux | Linux | 84b78514033ff22c443473214ab6d0508394cf7a |
| Linux | Linux | 4.0.2 |
| Linux | Linux | 4.1 |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
