CVE-2026-98983
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: unshare: don't drop active namespace references that were never taken Active references on the namespaces of an nsproxy are taken when the nsproxy is installed into a task in switch_task_namespaces() and copy_namespaces() and dropped again by put_nsproxy() through deactivate_nsproxy(). But ksys_unshare() calls put_nsproxy() on an nsproxy that was never installed when set_cred_ucounts() fails. The new namespaces of that nsproxy go from zero to minus one and the namespaces shared with the caller lose a reference that belongs to the nsproxy the caller keeps using: WARNING: kernel/nscommon.c:171 at __ns_ref_active_put+0x1cd/0x230 nsproxy_ns_active_put deactivate_nsproxy ksys_unshare Afterwards the namespaces the caller lives in aren't listed by listns() anymore. set_cred_ucounts() only fails when alloc_ucounts() can't allocate and it only allocates when the real uid of the caller differs from its effective uid. Commit cefd55bd2159 ("nsproxy: fix free_nsproxy() and simplify create_new_namespaces()") separated the two cases on purpose. nsproxy_free() frees an nsproxy that was prepared but never installed and that's what a failed setns() uses in put_nsset(). Export it and use it for a failed unshare() as well.
View original CVE JSON
{
"id": "CVE-2026-98983",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-10-23T13:17:20.160",
"lastModified": "2026-10-23T13:17:20.160",
"vulnStatus": "Received",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nunshare: don't drop active namespace references that were never taken\n\nActive references on the namespaces of an nsproxy are taken when the\nnsproxy is installed into a task in switch_task_namespaces() and\ncopy_namespaces() and dropped again by put_nsproxy() through\ndeactivate_nsproxy().\n\nBut ksys_unshare() calls put_nsproxy() on an nsproxy that was never\ninstalled when set_cred_ucounts() fails. The new namespaces of that\nnsproxy go from zero to minus one and the namespaces shared with the\ncaller lose a reference that belongs to the nsproxy the caller keeps\nusing:\n\n WARNING: kernel/nscommon.c:171 at __ns_ref_active_put+0x1cd/0x230\n nsproxy_ns_active_put\n deactivate_nsproxy\n ksys_unshare\n\nAfterwards the namespaces the caller lives in aren't listed by listns()\nanymore. set_cred_ucounts() only fails when alloc_ucounts() can't\nallocate and it only allocates when the real uid of the caller differs\nfrom its effective uid.\n\nCommit cefd55bd2159 (\"nsproxy: fix free_nsproxy() and simplify\ncreate_new_namespaces()\") separated the two cases on purpose.\nnsproxy_free() frees an nsproxy that was prepared but never installed\nand that's what a failed setns() uses in put_nsset(). Export it and use\nit for a failed unshare() as well."
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"include/linux/nsproxy.h",
"kernel/fork.c",
"kernel/nsproxy.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "a98621a0f187a934c115dcfe79a49520ae892111",
"lessThan": "56fe03a0c05dba4c5f6a23c391f96de1614a098c",
"versionType": "git",
"status": "affected"
},
{
"version": "a98621a0f187a934c115dcfe79a49520ae892111",
"lessThan": "0b6f31a3c0b16066f812e94b52a704174a6f23cd",
"versionType": "git",
"status": "affected"
},
{
"version": "27ae6b17c9ba7ff353ab0906297f08aa845782b4",
"versionType": "git",
"status": "affected"
},
{
"version": "297261b343371c4f0b31055d53d285138ec21565",
"versionType": "git",
"status": "affected"
},
{
"version": "813a47b0309097da71781ee4ac11922e39b67d55",
"versionType": "git",
"status": "affected"
},
{
"version": "6e608e3e5ce12ce7fd21e46212eccca37f917d0e",
"versionType": "git",
"status": "affected"
},
{
"version": "a261fccdb4ac58ec5ba6aa1d92a6cc418fff301f",
"versionType": "git",
"status": "affected"
},
{
"version": "665dc1ed16357988d439fc5bbc860ee36f540d81",
"versionType": "git",
"status": "affected"
},
{
"version": "5.15.209",
"lessThan": "5.16",
"versionType": "semver",
"status": "affected"
},
{
"version": "6.1.175",
"lessThan": "6.2",
"versionType": "semver",
"status": "affected"
},
{
"version": "6.6.141",
"lessThan": "6.7",
"versionType": "semver",
"status": "affected"
},
{
"version": "6.12.91",
"lessThan": "6.13",
"versionType": "semver",
"status": "affected"
},
{
"version": "6.18.33",
"lessThan": "6.19",
"versionType": "semver",
"status": "affected"
},
{
"version": "7.0.10",
"lessThan": "7.1",
"versionType": "semver",
"status": "affected"
}
]
},
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "affected",
"programFiles": [
"include/linux/nsproxy.h",
"kernel/fork.c",
"kernel/nsproxy.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "7.1",
"status": "affected"
},
{
"version": "0",
"lessThan": "7.1",
"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/0b6f31a3c0b16066f812e94b52a704174a6f23cd",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/56fe03a0c05dba4c5f6a23c391f96de1614a098c",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
]
}