{"id":"CVE-2026-72034","summary":"fhandle: reject detached mounts in capable_wrt_mount()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nfhandle: reject detached mounts in capable_wrt_mount()\n\nThe recent fhandle RCU fix moved the mount namespace capability check\ninto capable_wrt_mount(), so a non-NULL mnt_namespace survives the\nns_capable() dereference. The helper still assumes the later\nREAD_ONCE(mount-\u003emnt_ns) must be non-NULL because may_decode_fh()\nchecked is_mounted() first.\n\nThat assumption is not stable. A detached mount from\nopen_tree(..., OPEN_TREE_CLONE) can be dissolved on fput while\nopen_by_handle_at() is between those checks, and umount_tree() can\nclear mount-\u003emnt_ns. If the helper observes NULL, it dereferences\nmnt_ns-\u003euser_ns and panics.\n\nReturn false when the RCU read observes a detached mount. This keeps\nthe relaxed permission path conservative: a mount no longer attached\nto a namespace cannot authorize open_by_handle_at() access.","modified":"2026-08-18T03:56:19.095077076Z","published":"2026-08-15T05:51:55.739Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72034.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/15104234c267ebe04b9f9a73e5c2179cc265ff60"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6c52226072a3c61337b1eec1799bb987748884fa"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6c732471740bc2ac9b0946134f9f551dc75f4369"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6ee183d89261bf1d1cf9f06d80a40dab8f36ee55"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72034.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72034"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"620c266f394932e5decc4b34683a75dfc59dc2f4"},{"fixed":"15104234c267ebe04b9f9a73e5c2179cc265ff60"},{"fixed":"6c52226072a3c61337b1eec1799bb987748884fa"},{"fixed":"6ee183d89261bf1d1cf9f06d80a40dab8f36ee55"},{"fixed":"6c732471740bc2ac9b0946134f9f551dc75f4369"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72034.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.11.0"},{"fixed":"6.12.97"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.40"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.5"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72034.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}