CVE-2026-74483 (GCVE-0-2026-74483)
Vulnerability from cvelistv5
Published
2026-08-15 12:27
Modified
2026-08-23 12:47
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
binfmt_misc: don't leak the user namespace when the mount fails
bm_get_tree() takes a reference to the user namespace and hands it to
get_tree_keyed() as the sget key. sget_fc() moves that reference into
sb->s_fs_info and clears fc->s_fs_info, so from that point on the
superblock owns it and bm_free() doesn't see it anymore.
The superblock drops it in ->put_super(). But generic_shutdown_super()
only calls ->put_super() from inside the if (sb->s_root) branch, so
nothing releases it when bm_fill_super() fails:
- The kzalloc_obj() failure leaves s_root NULL and the whole branch is
skipped.
- A simple_fill_super() failure in the file loop leaves s_root set, but
s_op still points at simple_super_operations, which has no
->put_super(). bm_fill_super() installs s_ops only once
simple_fill_super() returned success, and installing it earlier
wouldn't help either because simple_fill_super() overwrites s_op.
Either way vfs_get_super() calls deactivate_locked_super() and the
reference is gone for good. binfmt_misc mounts are available in a user
namespace and both the inode and the dentry cache are SLAB_ACCOUNT, so
an unprivileged caller under a tight memory cgroup can fail
simple_fill_super() on demand and leak one user namespace per attempt.
Drop the reference in ->kill_sb() instead, which runs unconditionally,
the same way nfsd and rpc_pipefs release their keyed s_fs_info.
That also stops ->put_super() from clearing s_fs_info while the
superblock is still on @fs_supers. generic_shutdown_super() leaves it
there on purpose so that sget_fc() keeps finding it until kill_sb() has
run, but a NULL s_fs_info makes test_keyed_super() miss it, so a
concurrent mount for the same user namespace skips the grab_super()
wait and creates a second superblock for a namespace that is still
being torn down.
References
| URL | Tags | |
|---|---|---|
Impacted products
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"fs/binfmt_misc.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "ffec017158d3aad8a6ffca1dfad63d63bde9caad",
"status": "affected",
"version": "21ca59b365c091d583f36ac753eaa8baf947be6f",
"versionType": "git"
},
{
"lessThan": "867aed6a4848761190d5ebdedf9642648f97bceb",
"status": "affected",
"version": "21ca59b365c091d583f36ac753eaa8baf947be6f",
"versionType": "git"
},
{
"lessThan": "87a4eb9bbb3497f749bbac612af22ddaa62d7b0d",
"status": "affected",
"version": "21ca59b365c091d583f36ac753eaa8baf947be6f",
"versionType": "git"
},
{
"lessThan": "b8206f516fe7cbe785cf44bf09c17c438d7c3cad",
"status": "affected",
"version": "21ca59b365c091d583f36ac753eaa8baf947be6f",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"fs/binfmt_misc.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "6.7"
},
{
"lessThan": "6.7",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.105",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.46",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.8",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.105",
"versionStartIncluding": "6.7",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.46",
"versionStartIncluding": "6.7",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.1.8",
"versionStartIncluding": "6.7",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.2",
"versionStartIncluding": "6.7",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbinfmt_misc: don\u0027t leak the user namespace when the mount fails\n\nbm_get_tree() takes a reference to the user namespace and hands it to\nget_tree_keyed() as the sget key. sget_fc() moves that reference into\nsb-\u003es_fs_info and clears fc-\u003es_fs_info, so from that point on the\nsuperblock owns it and bm_free() doesn\u0027t see it anymore.\n\nThe superblock drops it in -\u003eput_super(). But generic_shutdown_super()\nonly calls -\u003eput_super() from inside the if (sb-\u003es_root) branch, so\nnothing releases it when bm_fill_super() fails:\n\n- The kzalloc_obj() failure leaves s_root NULL and the whole branch is\n skipped.\n\n- A simple_fill_super() failure in the file loop leaves s_root set, but\n s_op still points at simple_super_operations, which has no\n -\u003eput_super(). bm_fill_super() installs s_ops only once\n simple_fill_super() returned success, and installing it earlier\n wouldn\u0027t help either because simple_fill_super() overwrites s_op.\n\nEither way vfs_get_super() calls deactivate_locked_super() and the\nreference is gone for good. binfmt_misc mounts are available in a user\nnamespace and both the inode and the dentry cache are SLAB_ACCOUNT, so\nan unprivileged caller under a tight memory cgroup can fail\nsimple_fill_super() on demand and leak one user namespace per attempt.\n\nDrop the reference in -\u003ekill_sb() instead, which runs unconditionally,\nthe same way nfsd and rpc_pipefs release their keyed s_fs_info.\n\nThat also stops -\u003eput_super() from clearing s_fs_info while the\nsuperblock is still on @fs_supers. generic_shutdown_super() leaves it\nthere on purpose so that sget_fc() keeps finding it until kill_sb() has\nrun, but a NULL s_fs_info makes test_keyed_super() miss it, so a\nconcurrent mount for the same user namespace skips the grab_super()\nwait and creates a second superblock for a namespace that is still\nbeing torn down."
}
],
"providerMetadata": {
"dateUpdated": "2026-08-23T12:47:24.496Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/ffec017158d3aad8a6ffca1dfad63d63bde9caad"
},
{
"url": "https://git.kernel.org/stable/c/867aed6a4848761190d5ebdedf9642648f97bceb"
},
{
"url": "https://git.kernel.org/stable/c/87a4eb9bbb3497f749bbac612af22ddaa62d7b0d"
},
{
"url": "https://git.kernel.org/stable/c/b8206f516fe7cbe785cf44bf09c17c438d7c3cad"
}
],
"title": "binfmt_misc: don\u0027t leak the user namespace when the mount fails",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74483",
"datePublished": "2026-08-15T12:27:15.709Z",
"dateReserved": "2026-08-15T05:44:03.904Z",
"dateUpdated": "2026-08-23T12:47:24.496Z",
"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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