{"id":"CVE-2026-98989","state":"PUBLISHED","title":"namespace: check a recursive bind mount for mount namespace loops","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: check a recursive bind mount for mount namespace loops\n\ndo_loopback() refuses to bind mount the file of a mount namespace that\nis as old as the caller's or older because a mount namespace that holds\na mount of its own file, or of an ancestor's, would cause a cycle. But\nit only checks the dentry the bind mount starts from. With MS_REC\neverything below it is copied and do_loopback() passes\nCL_COPY_MNT_NS_FILE so mount namespace files below the source are\ncopied.\n\nThat's fine for a source in the caller's own mount namespace. Every\nmount namespace file in there passed the same check when it was\nbind-mounted. It isn't fine for a source in another mount namespace.\nmay_copy_tree() accepts a bind mount of any nsfs or pidfs file no matter\nwhat mount namespace it lives in so that /proc/<pid>/ns/<ns> and pidfds\ncan be bind mounted. If we create a bind-mount stack of mount namespaces\nfile descriptors the kernel will copy them irrespective of their\nancestoral relationship to the mount namespace in question:\n\n  151 146 0:7 net:[4026531833] /tmp/nrc/y rw - nsfs nsfs rw\n  152 151 0:7 mnt:[4026532293] /tmp/nrc/y rw - nsfs nsfs rw\n\nMount 152 is a mount of the mount namespace file of mount namespace\n4026532293 inside mount namespace 4026532293. That namespace and every\nmount in it are leaked... All it takes is a process in an older mount\nnamespace that stacks the file and repeating it leaks without limit:\n\n  after control: Shmem:               380 kB\n  child: mount(/proc/self/fd/6, MS_BIND|MS_REC): ok\n  after cycle: Shmem:             65916 kB\n\ndo_move_mount() runs check_for_nsfs_mounts() over a detached tree for\nexactly that reason. Do the same for the copy before it is grafted.","publishedAt":"2026-10-23T12:20:08.366Z","updatedAt":"2026-10-23T12:20:08.366Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"e149ed2b805fefdccf7ccdfc19eca22fdd4514ac","status":"affected","lessThan":"a0ba48256f5dff6f75a45f8ce39fe57f21df1022","versionType":"git"},{"version":"e149ed2b805fefdccf7ccdfc19eca22fdd4514ac","status":"affected","lessThan":"37a82f400efa4d263542a5fa41755b21057f1e5d","versionType":"git"},{"version":"e149ed2b805fefdccf7ccdfc19eca22fdd4514ac","status":"affected","lessThan":"c640a01a78e42302879006ed7b7d5a9a943ba815","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/namespace.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"3.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"3.19","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.11","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/namespace.c"]}],"references":["https://git.kernel.org/stable/c/a0ba48256f5dff6f75a45f8ce39fe57f21df1022","https://git.kernel.org/stable/c/37a82f400efa4d263542a5fa41755b21057f1e5d","https://git.kernel.org/stable/c/c640a01a78e42302879006ed7b7d5a9a943ba815"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98989.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98989","state":"PUBLISHED","datePublished":"2026-10-23T12:20:08.366Z","dateUpdated":"2026-10-23T12:20:08.366Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.384Z"},"containers":{"cna":{"title":"namespace: check a recursive bind mount for mount namespace loops","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: check a recursive bind mount for mount namespace loops\n\ndo_loopback() refuses to bind mount the file of a mount namespace that\nis as old as the caller's or older because a mount namespace that holds\na mount of its own file, or of an ancestor's, would cause a cycle. But\nit only checks the dentry the bind mount starts from. With MS_REC\neverything below it is copied and do_loopback() passes\nCL_COPY_MNT_NS_FILE so mount namespace files below the source are\ncopied.\n\nThat's fine for a source in the caller's own mount namespace. Every\nmount namespace file in there passed the same check when it was\nbind-mounted. It isn't fine for a source in another mount namespace.\nmay_copy_tree() accepts a bind mount of any nsfs or pidfs file no matter\nwhat mount namespace it lives in so that /proc/<pid>/ns/<ns> and pidfds\ncan be bind mounted. If we create a bind-mount stack of mount namespaces\nfile descriptors the kernel will copy them irrespective of their\nancestoral relationship to the mount namespace in question:\n\n  151 146 0:7 net:[4026531833] /tmp/nrc/y rw - nsfs nsfs rw\n  152 151 0:7 mnt:[4026532293] /tmp/nrc/y rw - nsfs nsfs rw\n\nMount 152 is a mount of the mount namespace file of mount namespace\n4026532293 inside mount namespace 4026532293. That namespace and every\nmount in it are leaked... All it takes is a process in an older mount\nnamespace that stacks the file and repeating it leaks without limit:\n\n  after control: Shmem:               380 kB\n  child: mount(/proc/self/fd/6, MS_BIND|MS_REC): ok\n  after cycle: Shmem:             65916 kB\n\ndo_move_mount() runs check_for_nsfs_mounts() over a detached tree for\nexactly that reason. Do the same for the copy before it is grafted."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"e149ed2b805fefdccf7ccdfc19eca22fdd4514ac","status":"affected","lessThan":"a0ba48256f5dff6f75a45f8ce39fe57f21df1022","versionType":"git"},{"version":"e149ed2b805fefdccf7ccdfc19eca22fdd4514ac","status":"affected","lessThan":"37a82f400efa4d263542a5fa41755b21057f1e5d","versionType":"git"},{"version":"e149ed2b805fefdccf7ccdfc19eca22fdd4514ac","status":"affected","lessThan":"c640a01a78e42302879006ed7b7d5a9a943ba815","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/namespace.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"3.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"3.19","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.11","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/namespace.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/a0ba48256f5dff6f75a45f8ce39fe57f21df1022"},{"url":"https://git.kernel.org/stable/c/37a82f400efa4d263542a5fa41755b21057f1e5d"},{"url":"https://git.kernel.org/stable/c/c640a01a78e42302879006ed7b7d5a9a943ba815"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-23T12:20:08.366Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.19","versionEndExcluding":"6.18.57"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.19","versionEndExcluding":"7.2.11"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.19","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}