{"api_version":"1","generated_at":"2026-10-25T03:40:27+00:00","cve":"CVE-2026-98987","urls":{"html":"https://cve.report/CVE-2026-98987","api":"https://cve.report/api/cve/CVE-2026-98987.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-98987","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-98987"},"summary":{"title":"namespace: look at the topmost mount for a mount namespace file","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: look at the topmost mount for a mount namespace file\n\nattach_recursive_mnt() preallocates a mountpoint for the root of the\ntopmost mount of the source so that a mount that already sits at the\ndestination can be put on top of the source or on top of one of its\npropagated copies.\n\nThe copies are made without CL_COPY_MNT_NS_FILE so their chain of\novermounts is shorter than the source's. It ends below the first bind\nmount of a mount namespace file. So while the loop walks up the chain of\nthe source it remembers the mountpoint of that mount in \"shorter\" and\nthe existing mount is put there for the copies.\n\nBut the loop ends at the topmost mount without ever looking at it. If\nthe topmost mount is the only mount namespace file in the chain\n\"shorter\" stays NULL and mnt_change_mountpoint() attaches the existing\nmount of the copy below the root of the mount namespace file. That's a\ndentry of nsfs. No path walk in the copy's mount namespace ever gets\nthere. The mount is gone until its parent goes and the copy that took\nits place can't be unmounted synchronously because it has a child:\n\n  S      bind mount of a file\n  N      bind mount of a mount namespace file on top of S\n  A      shared mount, B a slave of A, Q mounted on B/file\n\n  move_mount(S, A/file)\n  cat B/file          -> the content of S instead of Q\n  umount B/file       -> EBUSY\n\nLook at every mount of the chain including the topmost one.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-10-23 13:17:20","updated_at":"2026-10-23 13:17:20"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/8714b44adac7b10506e1db3ef1710689751f0f10","name":"https://git.kernel.org/stable/c/8714b44adac7b10506e1db3ef1710689751f0f10","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/b9c40553f6ceba50042281eef6f701e5fb719726","name":"https://git.kernel.org/stable/c/b9c40553f6ceba50042281eef6f701e5fb719726","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/87ecd4c6da146363384a603bd9e90c90e7275536","name":"https://git.kernel.org/stable/c/87ecd4c6da146363384a603bd9e90c90e7275536","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-98987","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98987","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 96f5d2e051653f2cfe9137c5d3c7794c358ffb03 b9c40553f6ceba50042281eef6f701e5fb719726 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 96f5d2e051653f2cfe9137c5d3c7794c358ffb03 87ecd4c6da146363384a603bd9e90c90e7275536 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 96f5d2e051653f2cfe9137c5d3c7794c358ffb03 8714b44adac7b10506e1db3ef1710689751f0f10 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.17","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.17 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.57 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.11 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["fs/namespace.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"b9c40553f6ceba50042281eef6f701e5fb719726","status":"affected","version":"96f5d2e051653f2cfe9137c5d3c7794c358ffb03","versionType":"git"},{"lessThan":"87ecd4c6da146363384a603bd9e90c90e7275536","status":"affected","version":"96f5d2e051653f2cfe9137c5d3c7794c358ffb03","versionType":"git"},{"lessThan":"8714b44adac7b10506e1db3ef1710689751f0f10","status":"affected","version":"96f5d2e051653f2cfe9137c5d3c7794c358ffb03","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["fs/namespace.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"6.17"},{"lessThan":"6.17","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.57","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.11","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.57","versionStartIncluding":"6.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.11","versionStartIncluding":"6.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3","versionStartIncluding":"6.17","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: look at the topmost mount for a mount namespace file\n\nattach_recursive_mnt() preallocates a mountpoint for the root of the\ntopmost mount of the source so that a mount that already sits at the\ndestination can be put on top of the source or on top of one of its\npropagated copies.\n\nThe copies are made without CL_COPY_MNT_NS_FILE so their chain of\novermounts is shorter than the source's. It ends below the first bind\nmount of a mount namespace file. So while the loop walks up the chain of\nthe source it remembers the mountpoint of that mount in \"shorter\" and\nthe existing mount is put there for the copies.\n\nBut the loop ends at the topmost mount without ever looking at it. If\nthe topmost mount is the only mount namespace file in the chain\n\"shorter\" stays NULL and mnt_change_mountpoint() attaches the existing\nmount of the copy below the root of the mount namespace file. That's a\ndentry of nsfs. No path walk in the copy's mount namespace ever gets\nthere. The mount is gone until its parent goes and the copy that took\nits place can't be unmounted synchronously because it has a child:\n\n  S      bind mount of a file\n  N      bind mount of a mount namespace file on top of S\n  A      shared mount, B a slave of A, Q mounted on B/file\n\n  move_mount(S, A/file)\n  cat B/file          -> the content of S instead of Q\n  umount B/file       -> EBUSY\n\nLook at every mount of the chain including the topmost one."}],"providerMetadata":{"dateUpdated":"2026-10-23T12:20:06.180Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/b9c40553f6ceba50042281eef6f701e5fb719726"},{"url":"https://git.kernel.org/stable/c/87ecd4c6da146363384a603bd9e90c90e7275536"},{"url":"https://git.kernel.org/stable/c/8714b44adac7b10506e1db3ef1710689751f0f10"}],"title":"namespace: look at the topmost mount for a mount namespace file","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-98987","datePublished":"2026-10-23T12:20:06.180Z","dateReserved":"2026-09-25T10:25:14.384Z","dateUpdated":"2026-10-23T12:20:06.180Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-23 13:17:20","lastModifiedDate":"2026-10-23 13:17:20","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"98987","Ordinal":"1","Title":"namespace: look at the topmost mount for a mount namespace file","CVE":"CVE-2026-98987","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"98987","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: look at the topmost mount for a mount namespace file\n\nattach_recursive_mnt() preallocates a mountpoint for the root of the\ntopmost mount of the source so that a mount that already sits at the\ndestination can be put on top of the source or on top of one of its\npropagated copies.\n\nThe copies are made without CL_COPY_MNT_NS_FILE so their chain of\novermounts is shorter than the source's. It ends below the first bind\nmount of a mount namespace file. So while the loop walks up the chain of\nthe source it remembers the mountpoint of that mount in \"shorter\" and\nthe existing mount is put there for the copies.\n\nBut the loop ends at the topmost mount without ever looking at it. If\nthe topmost mount is the only mount namespace file in the chain\n\"shorter\" stays NULL and mnt_change_mountpoint() attaches the existing\nmount of the copy below the root of the mount namespace file. That's a\ndentry of nsfs. No path walk in the copy's mount namespace ever gets\nthere. The mount is gone until its parent goes and the copy that took\nits place can't be unmounted synchronously because it has a child:\n\n  S      bind mount of a file\n  N      bind mount of a mount namespace file on top of S\n  A      shared mount, B a slave of A, Q mounted on B/file\n\n  move_mount(S, A/file)\n  cat B/file          -> the content of S instead of Q\n  umount B/file       -> EBUSY\n\nLook at every mount of the chain including the topmost one.","Type":"Description","Title":"namespace: look at the topmost mount for a mount namespace file"}]}}}