CVE-2026-74483
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:
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.
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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.
Detalles técnicos trazas, registros y código del informe original
- 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.
CVSS
NVD no ha asignado puntuación CVSS a esta CVE (habitual desde el cambio de política de abril de 2026).
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.21%
- Percentil entre todas las CVEs puntuadas: 10
- Fecha de la puntuación: 5/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
JSON original (NVD)
Mostrar
{
"id": "CVE-2026-74483",
"cveTags": [],
"metrics": {},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "21ca59b365c091d583f36ac753eaa8baf947be6f",
"lessThan": "ffec017158d3aad8a6ffca1dfad63d63bde9caad",
"versionType": "git"
},
{
"status": "affected",
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"versionType": "git"
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{
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"versionType": "git"
},
{
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"lessThan": "b8206f516fe7cbe785cf44bf09c17c438d7c3cad",
"versionType": "git"
}
],
"programFiles": [
"fs/binfmt_misc.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.7"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.7",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.12.105",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.46",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.1.8",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"fs/binfmt_misc.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-08-15T13:17:53.163",
"references": [
{
"url": "https://git.kernel.org/stable/c/867aed6a4848761190d5ebdedf9642648f97bceb",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/87a4eb9bbb3497f749bbac612af22ddaa62d7b0d",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/b8206f516fe7cbe785cf44bf09c17c438d7c3cad",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/ffec017158d3aad8a6ffca1dfad63d63bde9caad",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbinfmt_misc: don't 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->s_fs_info and clears fc->s_fs_info, so from that point on the\nsuperblock owns it and bm_free() doesn't see it anymore.\n\nThe superblock drops it in ->put_super(). But generic_shutdown_super()\nonly calls ->put_super() from inside the if (sb->s_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 ->put_super(). bm_fill_super() installs s_ops only once\n simple_fill_super() returned success, and installing it earlier\n wouldn't 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 ->kill_sb() instead, which runs unconditionally,\nthe same way nfsd and rpc_pipefs release their keyed s_fs_info.\n\nThat also stops ->put_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."
}
],
"lastModified": "2026-08-23T13:16:44.530",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}