{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-72034", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-09T03:40:39.901Z", "datePublished": "2026-08-15T05:51:55.739Z", "dateUpdated": "2026-10-16T15:53:17.001Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T05:39:37.172Z" }, "descriptions": [ { "lang": "en", "value": "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->mnt_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->mnt_ns. If the helper observes NULL, it dereferences\nmnt_ns->user_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." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - Exploitation requires local syscalls only: open_tree(OPEN_TREE_CLONE) to obtain a detached mount fd, open_by_handle_at() to enter may_decode_fh()/capable_wrt_mount(), and close()/fput to dissolve the mount; no network, adjacent, or physical interface reaches this VFS fhandle path.\nAC:L - The attacker controls both sides of the TOCTOU race by concurrently calling open_by_handle_at() on a detached mount fd while another thread closes that fd (or a dup) to trigger dissolve_on_fput()/umount_tree() clearing mount->mnt_ns, making success depend on attacker timing rather than external state.\nPR:L - The relaxed permission path requires CAP_SYS_ADMIN in the current mount namespace (may_mount/open_tree) and CAP_DAC_READ_SEARCH in the current user namespace while lacking init_user_ns CAP_DAC_READ_SEARCH; these are obtainable by an unprivileged local user via user/mount namespaces (unshare -Urn), not real init-namespace root.\nUI:N - No victim action is required; the attacker creates the detached mount, supplies the file handle, and drives the concurrent open_by_handle_at()/close race entirely through their own syscalls and threads.\nS:U - Impact is confined to kernel memory/availability within the same security authority (local/container-triggered kernel panic or namespace lifetime corruption); it does not cross a VM escape, sandbox, or IOMMU boundary per kernel CVSS scope guidance.\nC:H - The affected window (since 620c266f3949) includes unsynchronized mount::mnt_ns access that can UAF freed mnt_namespace memory before the RCU fix, and later NULL/stale namespace dereferences; per kernel guidance UAF and mount-namespace lifetime races enable arbitrary kernel memory disclosure.\nI:H - Concurrent umount_tree() clearing mount->mnt_ns while capable_wrt_mount() dereferences mnt_ns->user_ns is a mount-namespace lifetime corruption bug; UAF in the same code path can be leveraged for heap corruption and arbitrary kernel writes/code execution, not merely a benign error return.\nA:H - Observing NULL or freed mnt_ns during ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) causes a kernel oops/panic; the race is repeatable by reopening detached mounts, enabling reliable host DoS from containerized tenants on multi-tenant cloud nodes." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/fhandle.c" ], "versions": [ { "version": "620c266f394932e5decc4b34683a75dfc59dc2f4", "lessThan": "15104234c267ebe04b9f9a73e5c2179cc265ff60", "status": "affected", "versionType": "git" }, { "version": "620c266f394932e5decc4b34683a75dfc59dc2f4", "lessThan": "6c52226072a3c61337b1eec1799bb987748884fa", "status": "affected", "versionType": "git" }, { "version": "620c266f394932e5decc4b34683a75dfc59dc2f4", "lessThan": "6ee183d89261bf1d1cf9f06d80a40dab8f36ee55", "status": "affected", "versionType": "git" }, { "version": "620c266f394932e5decc4b34683a75dfc59dc2f4", "lessThan": "6c732471740bc2ac9b0946134f9f551dc75f4369", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/fhandle.c" ], "versions": [ { "version": "6.11", "status": "affected" }, { "version": "0", "lessThan": "6.11", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.97", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.40", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.5", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.11", "versionEndExcluding": "6.12.97" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.11", "versionEndExcluding": "6.18.40" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.11", "versionEndExcluding": "7.1.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.11", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/15104234c267ebe04b9f9a73e5c2179cc265ff60" }, { "url": "https://git.kernel.org/stable/c/6c52226072a3c61337b1eec1799bb987748884fa" }, { "url": "https://git.kernel.org/stable/c/6ee183d89261bf1d1cf9f06d80a40dab8f36ee55" }, { "url": "https://git.kernel.org/stable/c/6c732471740bc2ac9b0946134f9f551dc75f4369" } ], "title": "fhandle: reject detached mounts in capable_wrt_mount()", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2026-72034", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "total" } ], "version": "2.0.3", "timestamp": "2026-10-16T15:50:22.071900Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T15:53:17.001Z" } } ] } }