CVE-2026-98982
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: namespace: don't let a pseudo dentry become the root of a mount d_alloc_pseudo() hands out dentries for pipes, sockets and other files that are never anyone's child or parent. They carry DCACHE_NORCU and dentry_free() frees them right away because no lockless path walk can ever reach them. That holds as long as such a dentry isn't the root of a mount. But bind mounting /proc/self/fd/<fd> of such a file does exactly that. Most callers of alloc_file_pseudo() put their files on kernel-internal mounts and may_copy_tree() refuses those. bpf_token_create() doesn't. It places the token file on the bpffs mount the caller handed it and that mount is in the caller's mount namespace so the clone goes through: mount --bind /proc/self/fd/<token> <file> open_tree(tokfd, "", AT_EMPTY_PATH | OPEN_TREE_CLONE) + move_mount() __follow_mount_rcu() then loads ->mnt_root of that mount, reads d_seq and d_flags of the dentry and only then checks mount_lock. The dentry can be gone by then. The final mntput() of an unmounted parent unhooks a child that stayed attached to it under mount_lock alone. When the child's holder does the final put right after that the root is dput() and freed immediately while a walker that found the mount hashed still looks at it. Refuse to clone a mount with a DCACHE_NORCU dentry as its root. Nothing sensible can be done with a bind mount of a bpf token anyway.
View original CVE JSON
{
"id": "CVE-2026-98982",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-10-23T13:17:20.043",
"lastModified": "2026-10-24T14:16:50.850",
"vulnStatus": "Received",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: don't let a pseudo dentry become the root of a mount\n\nd_alloc_pseudo() hands out dentries for pipes, sockets and other files\nthat are never anyone's child or parent. They carry DCACHE_NORCU and\ndentry_free() frees them right away because no lockless path walk can\never reach them. That holds as long as such a dentry isn't the root of\na mount. But bind mounting /proc/self/fd/<fd> of such a file does\nexactly that.\n\nMost callers of alloc_file_pseudo() put their files on kernel-internal\nmounts and may_copy_tree() refuses those. bpf_token_create() doesn't. It\nplaces the token file on the bpffs mount the caller handed it and that\nmount is in the caller's mount namespace so the clone goes through:\n\n mount --bind /proc/self/fd/<token> <file>\n open_tree(tokfd, \"\", AT_EMPTY_PATH | OPEN_TREE_CLONE) + move_mount()\n\n__follow_mount_rcu() then loads ->mnt_root of that mount, reads d_seq\nand d_flags of the dentry and only then checks mount_lock. The dentry\ncan be gone by then. The final mntput() of an unmounted parent unhooks\na child that stayed attached to it under mount_lock alone. When the\nchild's holder does the final put right after that the root is dput()\nand freed immediately while a walker that found the mount hashed still\nlooks at it.\n\nRefuse to clone a mount with a DCACHE_NORCU dentry as its root. Nothing\nsensible can be done with a bind mount of a bpf token anyway."
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"fs/namespace.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "35f96de04127d332a5c5e8a155d31f452f88c76d",
"lessThan": "a256e31e0c54c4c37d2523aa52faabdcdd2ebc07",
"versionType": "git",
"status": "affected"
},
{
"version": "35f96de04127d332a5c5e8a155d31f452f88c76d",
"lessThan": "7e1c466011ba9e64d43075396badc03191bcee44",
"versionType": "git",
"status": "affected"
},
{
"version": "35f96de04127d332a5c5e8a155d31f452f88c76d",
"lessThan": "00287afa7cd989efdbf5822b7efac33cce7d489a",
"versionType": "git",
"status": "affected"
},
{
"version": "35f96de04127d332a5c5e8a155d31f452f88c76d",
"lessThan": "b138e16fb1e81376cea89f727dda7bfccd140de4",
"versionType": "git",
"status": "affected"
}
]
},
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "affected",
"programFiles": [
"fs/namespace.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "6.9",
"status": "affected"
},
{
"version": "0",
"lessThan": "6.9",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.12.113",
"lessThanOrEqual": "6.12.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.18.57",
"lessThanOrEqual": "6.18.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.2.11",
"lessThanOrEqual": "7.2.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.3",
"lessThanOrEqual": "*",
"versionType": "original_commit_for_fix",
"status": "unaffected"
}
]
}
]
}
],
"metrics": {
"cvssMetricV31": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary",
"cvssData": {
"version": "3.1",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"attackVector": "LOCAL",
"attackComplexity": "LOW",
"privilegesRequired": "LOW",
"userInteraction": "NONE",
"scope": "UNCHANGED",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"availabilityImpact": "HIGH"
},
"exploitabilityScore": 1.8,
"impactScore": 5.9
}
]
},
"references": [
{
"url": "https://git.kernel.org/stable/c/00287afa7cd989efdbf5822b7efac33cce7d489a",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/7e1c466011ba9e64d43075396badc03191bcee44",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/a256e31e0c54c4c37d2523aa52faabdcdd2ebc07",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/b138e16fb1e81376cea89f727dda7bfccd140de4",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
]
}