{"api_version":"1","generated_at":"2026-08-22T19:29:53+00:00","cve":"CVE-2026-74618","urls":{"html":"https://cve.report/CVE-2026-74618","api":"https://cve.report/api/cve/CVE-2026-74618.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-74618","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-74618"},"summary":{"title":"binfmt_misc: don't warn when the mount is completed from another user namespace","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbinfmt_misc: don't warn when the mount is completed from another user namespace\n\nfsopen() records the caller's user namespace in fc->user_ns and hands\nback an ordinary file descriptor. Nothing ties the task that calls\nfsconfig(FSCONFIG_CMD_CREATE) to the task that created the context. The\nfd is inherited across fork() and exec() and it can be passed over a\nunix socket.\n\nCompleting a context from another user namespace is allowed on purpose.\nvfs_cmd_create() authorizes the create with mount_capable(), which for\nFS_USERNS_MOUNT checks ns_capable(fc->user_ns, CAP_SYS_ADMIN), and that\nsucceeds for a task holding CAP_SYS_ADMIN in an ancestor of fc->user_ns.\nSo an unprivileged task can reach the WARN_ON() in bm_fill_super():\ncreate a user and a mount namespace in a child, call\nfsopen(\"binfmt_misc\") there, send the fscontext fd to the parent and let\nthe parent issue FSCONFIG_CMD_CREATE. Both namespaces come from a plain\nunshare(1) and no capability is needed anywhere:\n\n  WARNING: fs/binfmt_misc.c:938 at bm_fill_super+0xa2/0xc0 [binfmt_misc]\n  CPU: 15 UID: 1000 PID: 3243382 Comm: fswarn\n  Call Trace:\n   get_tree_keyed+0x7d/0xb0\n   bm_get_tree+0x34/0x90 [binfmt_misc]\n   vfs_get_tree+0x2a/0x100\n   vfs_cmd_create+0x60/0xf0\n   __do_sys_fsconfig+0x4b2/0x500\n\nThe child needs the mount namespace because fsopen() itself gates on\nmay_mount(), which asks for CAP_SYS_ADMIN in the user namespace owning\nthe caller's mount namespace. fsconfig() doesn't repeat that check.\n\nIt is a WARN_ON() and not a WARN_ON_ONCE(), so the condition can be\nraised in a loop to taint the kernel and flood the log, and it panics a\nkernel booted with panic_on_warn.\n\nKeep refusing the mount and stop warning about it. Nothing in\nbm_fill_super() depends on the two namespaces matching, it derives\neverything from sb->s_user_ns.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-08-22 16:16:34","updated_at":"2026-08-22 16:16:34"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/24e95a24f151ce40d5fc1b3a6cefbcda8ded736c","name":"https://git.kernel.org/stable/c/24e95a24f151ce40d5fc1b3a6cefbcda8ded736c","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/047f927f54c6c17593e93aafe82dcb7acdda2a71","name":"https://git.kernel.org/stable/c/047f927f54c6c17593e93aafe82dcb7acdda2a71","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/37cf5cf1320a84a17225a1690547b8a0812ca94e","name":"https://git.kernel.org/stable/c/37cf5cf1320a84a17225a1690547b8a0812ca94e","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/79fdf39f1a31f88cb3833b6f8091fbf6acdca2c6","name":"https://git.kernel.org/stable/c/79fdf39f1a31f88cb3833b6f8091fbf6acdca2c6","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-74618","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-74618","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 21ca59b365c091d583f36ac753eaa8baf947be6f 37cf5cf1320a84a17225a1690547b8a0812ca94e git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 21ca59b365c091d583f36ac753eaa8baf947be6f 24e95a24f151ce40d5fc1b3a6cefbcda8ded736c git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 21ca59b365c091d583f36ac753eaa8baf947be6f 047f927f54c6c17593e93aafe82dcb7acdda2a71 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 21ca59b365c091d583f36ac753eaa8baf947be6f 79fdf39f1a31f88cb3833b6f8091fbf6acdca2c6 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.7","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.7 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.104 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.45 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.1.9 7.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2 * 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/binfmt_misc.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"37cf5cf1320a84a17225a1690547b8a0812ca94e","status":"affected","version":"21ca59b365c091d583f36ac753eaa8baf947be6f","versionType":"git"},{"lessThan":"24e95a24f151ce40d5fc1b3a6cefbcda8ded736c","status":"affected","version":"21ca59b365c091d583f36ac753eaa8baf947be6f","versionType":"git"},{"lessThan":"047f927f54c6c17593e93aafe82dcb7acdda2a71","status":"affected","version":"21ca59b365c091d583f36ac753eaa8baf947be6f","versionType":"git"},{"lessThan":"79fdf39f1a31f88cb3833b6f8091fbf6acdca2c6","status":"affected","version":"21ca59b365c091d583f36ac753eaa8baf947be6f","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["fs/binfmt_misc.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"6.7"},{"lessThan":"6.7","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.104","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.45","versionType":"semver"},{"lessThanOrEqual":"7.1.*","status":"unaffected","version":"7.1.9","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.2","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.104","versionStartIncluding":"6.7","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.45","versionStartIncluding":"6.7","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.1.9","versionStartIncluding":"6.7","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2","versionStartIncluding":"6.7","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nbinfmt_misc: don't warn when the mount is completed from another user namespace\n\nfsopen() records the caller's user namespace in fc->user_ns and hands\nback an ordinary file descriptor. Nothing ties the task that calls\nfsconfig(FSCONFIG_CMD_CREATE) to the task that created the context. The\nfd is inherited across fork() and exec() and it can be passed over a\nunix socket.\n\nCompleting a context from another user namespace is allowed on purpose.\nvfs_cmd_create() authorizes the create with mount_capable(), which for\nFS_USERNS_MOUNT checks ns_capable(fc->user_ns, CAP_SYS_ADMIN), and that\nsucceeds for a task holding CAP_SYS_ADMIN in an ancestor of fc->user_ns.\nSo an unprivileged task can reach the WARN_ON() in bm_fill_super():\ncreate a user and a mount namespace in a child, call\nfsopen(\"binfmt_misc\") there, send the fscontext fd to the parent and let\nthe parent issue FSCONFIG_CMD_CREATE. Both namespaces come from a plain\nunshare(1) and no capability is needed anywhere:\n\n  WARNING: fs/binfmt_misc.c:938 at bm_fill_super+0xa2/0xc0 [binfmt_misc]\n  CPU: 15 UID: 1000 PID: 3243382 Comm: fswarn\n  Call Trace:\n   get_tree_keyed+0x7d/0xb0\n   bm_get_tree+0x34/0x90 [binfmt_misc]\n   vfs_get_tree+0x2a/0x100\n   vfs_cmd_create+0x60/0xf0\n   __do_sys_fsconfig+0x4b2/0x500\n\nThe child needs the mount namespace because fsopen() itself gates on\nmay_mount(), which asks for CAP_SYS_ADMIN in the user namespace owning\nthe caller's mount namespace. fsconfig() doesn't repeat that check.\n\nIt is a WARN_ON() and not a WARN_ON_ONCE(), so the condition can be\nraised in a loop to taint the kernel and flood the log, and it panics a\nkernel booted with panic_on_warn.\n\nKeep refusing the mount and stop warning about it. Nothing in\nbm_fill_super() depends on the two namespaces matching, it derives\neverything from sb->s_user_ns."}],"providerMetadata":{"dateUpdated":"2026-08-22T15:32:02.778Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/37cf5cf1320a84a17225a1690547b8a0812ca94e"},{"url":"https://git.kernel.org/stable/c/24e95a24f151ce40d5fc1b3a6cefbcda8ded736c"},{"url":"https://git.kernel.org/stable/c/047f927f54c6c17593e93aafe82dcb7acdda2a71"},{"url":"https://git.kernel.org/stable/c/79fdf39f1a31f88cb3833b6f8091fbf6acdca2c6"}],"title":"binfmt_misc: don't warn when the mount is completed from another user namespace","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-74618","datePublished":"2026-08-22T15:32:02.778Z","dateReserved":"2026-08-15T05:44:03.921Z","dateUpdated":"2026-08-22T15:32:02.778Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-08-22 16:16:34","lastModifiedDate":"2026-08-22 16:16:34","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"74618","Ordinal":"1","Title":"binfmt_misc: don't warn when the mount is completed from another","CVE":"CVE-2026-74618","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"74618","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nbinfmt_misc: don't warn when the mount is completed from another user namespace\n\nfsopen() records the caller's user namespace in fc->user_ns and hands\nback an ordinary file descriptor. Nothing ties the task that calls\nfsconfig(FSCONFIG_CMD_CREATE) to the task that created the context. The\nfd is inherited across fork() and exec() and it can be passed over a\nunix socket.\n\nCompleting a context from another user namespace is allowed on purpose.\nvfs_cmd_create() authorizes the create with mount_capable(), which for\nFS_USERNS_MOUNT checks ns_capable(fc->user_ns, CAP_SYS_ADMIN), and that\nsucceeds for a task holding CAP_SYS_ADMIN in an ancestor of fc->user_ns.\nSo an unprivileged task can reach the WARN_ON() in bm_fill_super():\ncreate a user and a mount namespace in a child, call\nfsopen(\"binfmt_misc\") there, send the fscontext fd to the parent and let\nthe parent issue FSCONFIG_CMD_CREATE. Both namespaces come from a plain\nunshare(1) and no capability is needed anywhere:\n\n  WARNING: fs/binfmt_misc.c:938 at bm_fill_super+0xa2/0xc0 [binfmt_misc]\n  CPU: 15 UID: 1000 PID: 3243382 Comm: fswarn\n  Call Trace:\n   get_tree_keyed+0x7d/0xb0\n   bm_get_tree+0x34/0x90 [binfmt_misc]\n   vfs_get_tree+0x2a/0x100\n   vfs_cmd_create+0x60/0xf0\n   __do_sys_fsconfig+0x4b2/0x500\n\nThe child needs the mount namespace because fsopen() itself gates on\nmay_mount(), which asks for CAP_SYS_ADMIN in the user namespace owning\nthe caller's mount namespace. fsconfig() doesn't repeat that check.\n\nIt is a WARN_ON() and not a WARN_ON_ONCE(), so the condition can be\nraised in a loop to taint the kernel and flood the log, and it panics a\nkernel booted with panic_on_warn.\n\nKeep refusing the mount and stop warning about it. Nothing in\nbm_fill_super() depends on the two namespaces matching, it derives\neverything from sb->s_user_ns.","Type":"Description","Title":"binfmt_misc: don't warn when the mount is completed from another"}]}}}