{"id":"CVE-2026-98983","revision":"843d642fc8954ea1b6ee98e7d6a4cc91","records":[{"revision":"843d642fc8954ea1b6ee98e7d6a4cc91","observedAt":"2026-10-23T16:01:20.601+00:00","statement":{"source":"cve-program","id":"CVE-2026-98983","aliases":[],"title":"unshare: don't drop active namespace references that were never taken","description":"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.","state":0,"publishedAt":"2026-10-23T12:20:00.918+00:00","modifiedAt":"2026-10-23T12:20:00.918+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"include/linux/nsproxy.h\",\n                        \"kernel/fork.c\",\n                        \"kernel/nsproxy.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"a98621a0f187a934c115dcfe79a49520ae892111\",\n                            \"lessThan\": \"56fe03a0c05dba4c5f6a23c391f96de1614a098c\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"a98621a0f187a934c115dcfe79a49520ae892111\",\n                            \"lessThan\": \"0b6f31a3c0b16066f812e94b52a704174a6f23cd\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"27ae6b17c9ba7ff353ab0906297f08aa845782b4\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"297261b343371c4f0b31055d53d285138ec21565\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"813a47b0309097da71781ee4ac11922e39b67d55\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"6e608e3e5ce12ce7fd21e46212eccca37f917d0e\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"a261fccdb4ac58ec5ba6aa1d92a6cc418fff301f\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"665dc1ed16357988d439fc5bbc860ee36f540d81\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"5.15.209\",\n                            \"lessThan\": \"5.16\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.175\",\n                            \"lessThan\": \"6.2\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.141\",\n                            \"lessThan\": \"6.7\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.91\",\n                            \"lessThan\": \"6.13\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.33\",\n                            \"lessThan\": \"6.19\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.0.10\",\n                            \"lessThan\": \"7.1\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"include/linux/nsproxy.h\",\n                        \"kernel/fork.c\",\n                        \"kernel/nsproxy.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"7.1\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"7.1\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2.11\",\n                            \"lessThanOrEqual\": \"7.2.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.3\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[],"references":["https://git.kernel.org/stable/c/56fe03a0c05dba4c5f6a23c391f96de1614a098c","https://git.kernel.org/stable/c/0b6f31a3c0b16066f812e94b52a704174a6f23cd"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98983","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-98983","identifiers":["CVE-2026-98983"]},"retained":false,"historicalAffected":[]}],"coverage":[]}