CVE-2026-98989
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: namespace: check a recursive bind mount for mount namespace loops do_loopback() refuses to bind mount the file of a mount namespace that is as old as the caller's or older because a mount namespace that holds a mount of its own file, or of an ancestor's, would cause a cycle. But it only checks the dentry the bind mount starts from. With MS_REC everything below it is copied and do_loopback() passes CL_COPY_MNT_NS_FILE so mount namespace files below the source are copied. That's fine for a source in the caller's own mount namespace. Every mount namespace file in there passed the same check when it was bind-mounted. It isn't fine for a source in another mount namespace. may_copy_tree() accepts a bind mount of any nsfs or pidfs file no matter what mount namespace it lives in so that /proc/<pid>/ns/<ns> and pidfds can be bind mounted. If we create a bind-mount stack of mount namespaces file descriptors the kernel will copy them irrespective of their ancestoral relationship to the mount namespace in question: 151 146 0:7 net:[4026531833] /tmp/nrc/y rw - nsfs nsfs rw 152 151 0:7 mnt:[4026532293] /tmp/nrc/y rw - nsfs nsfs rw Mount 152 is a mount of the mount namespace file of mount namespace 4026532293 inside mount namespace 4026532293. That namespace and every mount in it are leaked... All it takes is a process in an older mount namespace that stacks the file and repeating it leaks without limit: after control: Shmem: 380 kB child: mount(/proc/self/fd/6, MS_BIND|MS_REC): ok after cycle: Shmem: 65916 kB do_move_mount() runs check_for_nsfs_mounts() over a detached tree for exactly that reason. Do the same for the copy before it is grafted.
View original CVE JSON
{
"id": "CVE-2026-98989",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-10-23T13:17:20.863",
"lastModified": "2026-10-23T13:17:20.863",
"vulnStatus": "Received",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: check a recursive bind mount for mount namespace loops\n\ndo_loopback() refuses to bind mount the file of a mount namespace that\nis as old as the caller's or older because a mount namespace that holds\na mount of its own file, or of an ancestor's, would cause a cycle. But\nit only checks the dentry the bind mount starts from. With MS_REC\neverything below it is copied and do_loopback() passes\nCL_COPY_MNT_NS_FILE so mount namespace files below the source are\ncopied.\n\nThat's fine for a source in the caller's own mount namespace. Every\nmount namespace file in there passed the same check when it was\nbind-mounted. It isn't fine for a source in another mount namespace.\nmay_copy_tree() accepts a bind mount of any nsfs or pidfs file no matter\nwhat mount namespace it lives in so that /proc/<pid>/ns/<ns> and pidfds\ncan be bind mounted. If we create a bind-mount stack of mount namespaces\nfile descriptors the kernel will copy them irrespective of their\nancestoral relationship to the mount namespace in question:\n\n 151 146 0:7 net:[4026531833] /tmp/nrc/y rw - nsfs nsfs rw\n 152 151 0:7 mnt:[4026532293] /tmp/nrc/y rw - nsfs nsfs rw\n\nMount 152 is a mount of the mount namespace file of mount namespace\n4026532293 inside mount namespace 4026532293. That namespace and every\nmount in it are leaked... All it takes is a process in an older mount\nnamespace that stacks the file and repeating it leaks without limit:\n\n after control: Shmem: 380 kB\n child: mount(/proc/self/fd/6, MS_BIND|MS_REC): ok\n after cycle: Shmem: 65916 kB\n\ndo_move_mount() runs check_for_nsfs_mounts() over a detached tree for\nexactly that reason. Do the same for the copy before it is grafted."
}
],
"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": "e149ed2b805fefdccf7ccdfc19eca22fdd4514ac",
"lessThan": "a0ba48256f5dff6f75a45f8ce39fe57f21df1022",
"versionType": "git",
"status": "affected"
},
{
"version": "e149ed2b805fefdccf7ccdfc19eca22fdd4514ac",
"lessThan": "37a82f400efa4d263542a5fa41755b21057f1e5d",
"versionType": "git",
"status": "affected"
},
{
"version": "e149ed2b805fefdccf7ccdfc19eca22fdd4514ac",
"lessThan": "c640a01a78e42302879006ed7b7d5a9a943ba815",
"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": "3.19",
"status": "affected"
},
{
"version": "0",
"lessThan": "3.19",
"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": {},
"references": [
{
"url": "https://git.kernel.org/stable/c/37a82f400efa4d263542a5fa41755b21057f1e5d",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/a0ba48256f5dff6f75a45f8ce39fe57f21df1022",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/c640a01a78e42302879006ed7b7d5a9a943ba815",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
]
}