unshare: don't drop active namespace references that were never taken
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.
CVE-2026-98983
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-98983
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"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"
}
],
"programFiles": [
"include/linux/nsproxy.h",
"kernel/fork.c",
"kernel/nsproxy.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "7.1"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "7.1",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "7.2.11",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"include/linux/nsproxy.h",
"kernel/fork.c",
"kernel/nsproxy.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-98983
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #52832 · Revision 1
- Added to Heist Feed
- Publisher date