CVE-2026-98990 (GCVE-0-2026-98990)
Vulnerability from cvelistv5
Published
2026-10-23 12:20
Modified
2026-10-30 12:40
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
namespace: check a submount for references right before unmounting it
shrink_submounts() and mark_mounts_for_expiry() first collect all the
mounts they are allowed to unmount and then unmount them.
Whether a mount is busy is decided by propagate_mount_busy() on the
tree. But unmounting the first mount changes the tree that the second
one propagates into. propagate_umount()
moves a surviving overmount off a copy it unmounts and mounts it where
the copy was mounted. If that's where the propagated copy of the second
victim is looked up the overmount becomes a candidate of the second
umount_tree(). It's childless and so trim_one() commits it without
looking at its reference count.
So a synchronous umount pulls out a busy mount that is in use somewhere
else and marks it MNT_SYNC_UMOUNT while it has users:
umount2(/tmp/plshrink/p1, 0) = 0 errno 0
cwd is (unreachable)
The same two umounts requested one after the other fail with EBUSY.
This needs a mount with MNT_SHRINKABLE, i.e., automounted submounts of
NFS, AFS and CIFS or the tracefs mount below debugfs. Bind mounts
inherit the flag.
Check each mount right before it is unmounted under the same hold of
namespace_sem and mount_lock as the umount itself. Make sure that the
algorithm stays linear.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 1064f874abc0d05eeed8993815f584d847b72486 Version: 1064f874abc0d05eeed8993815f584d847b72486 Version: 1064f874abc0d05eeed8993815f584d847b72486 Version: 1064f874abc0d05eeed8993815f584d847b72486 Version: 1064f874abc0d05eeed8993815f584d847b72486 Version: 1064f874abc0d05eeed8993815f584d847b72486 Version: 1064f874abc0d05eeed8993815f584d847b72486 Version: 1064f874abc0d05eeed8993815f584d847b72486 Version: 5e6ef5ef6eaf690faad3a7c6c665ebf45d7b6ccf Version: 839d42687dfce0ed0ea2c6bd8d707cc0e276fbe7 Version: 808e83e5add13152bd4a88346487de68395c136b Version: 6de9d08a9718ee9c12ba6343c50141c2d633e3dc Version: 4.1.40 ≤ Version: 4.4.54 ≤ Version: 4.9.15 ≤ Version: 4.10.3 ≤ |
||
{
"containers": {
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"programFiles": [
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]
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{
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]
}
],
"cpeApplicability": [
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],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: check a submount for references right before unmounting it\n\nshrink_submounts() and mark_mounts_for_expiry() first collect all the\nmounts they are allowed to unmount and then unmount them.\n\nWhether a mount is busy is decided by propagate_mount_busy() on the\ntree. But unmounting the first mount changes the tree that the second\none propagates into. propagate_umount()\nmoves a surviving overmount off a copy it unmounts and mounts it where\nthe copy was mounted. If that\u0027s where the propagated copy of the second\nvictim is looked up the overmount becomes a candidate of the second\numount_tree(). It\u0027s childless and so trim_one() commits it without\nlooking at its reference count.\n\nSo a synchronous umount pulls out a busy mount that is in use somewhere\nelse and marks it MNT_SYNC_UMOUNT while it has users:\n\n umount2(/tmp/plshrink/p1, 0) = 0 errno 0\n cwd is (unreachable)\n\nThe same two umounts requested one after the other fail with EBUSY.\nThis needs a mount with MNT_SHRINKABLE, i.e., automounted submounts of\nNFS, AFS and CIFS or the tracefs mount below debugfs. Bind mounts\ninherit the flag.\n\nCheck each mount right before it is unmounted under the same hold of\nnamespace_sem and mount_lock as the umount itself. Make sure that the\nalgorithm stays linear."
}
],
"providerMetadata": {
"dateUpdated": "2026-10-30T12:40:44.542Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/cda0c4e502a0f74a191471ce100fb061e5ab35d6"
},
{
"url": "https://git.kernel.org/stable/c/3f55f71291e4332983cd63b288d1f2be3c9c08fc"
},
{
"url": "https://git.kernel.org/stable/c/361f59e7f3f9a219fb5567bf9abc8482a154a399"
},
{
"url": "https://git.kernel.org/stable/c/f6394281834492c6516a405a348b545ae698a331"
},
{
"url": "https://git.kernel.org/stable/c/6e4012e571867868b545c91ca9d6095fdb709907"
},
{
"url": "https://git.kernel.org/stable/c/d73f04e92c1aab78d96ac6cadb234c8a3a373d22"
},
{
"url": "https://git.kernel.org/stable/c/18902a23ef36f83d32bafc58ae2484e6bb4bb8ef"
},
{
"url": "https://git.kernel.org/stable/c/32bf92416614a1e3ff3524fc6b780259c7aad3ef"
}
],
"title": "namespace: check a submount for references right before unmounting it",
"x_generator": {
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}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-98990",
"datePublished": "2026-10-23T12:20:09.349Z",
"dateReserved": "2026-09-25T10:25:14.384Z",
"dateUpdated": "2026-10-30T12:40:44.542Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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