{"id":"CVE-2026-74619","title":"In the Linux kernel, the following vulnerability has been resolved:\n\novl: 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 des…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\novl: 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 des…","severity":"none","published":"2026-08-22","updated":"2026-10-14","sourceUpdated":"2026-10-14T13:10:00.187","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-74619","references":[{"url":"https://git.kernel.org/stable/c/42d99fcd8006007e2f708bede6789f37f3910b30","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/494346f2aab2489d379d43ff614aea447cf4e94d","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/513478092966dc9818d96dd2b3ed613fd2f6e30e","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/63981fc786daaa626cb14d9be1406f674d79f98f","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/be161fa31e3e9cc828a3c1bd935edca461e8a7a1","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd"],"epss":0.00168,"epssPercentile":0.05628,"ingestedAt":"2026-10-14T13:30:58.517Z","slug":"CVE-2026-74619","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\novl: 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 ovl_fill_super():\ncreate a user and a mount namespace in a child, call fsopen(\"overlay\")\nthere, send the fscontext fd to the parent and let the parent issue\nFSCONFIG_CMD_CREATE. Both namespaces come from a plain unshare(1) and no\ncapability is needed anywhere:\n\n  WARNING: fs/overlayfs/super.c:1551 at ovl_fill_super+0x7b9/0x1e20 [overlay]\n  CPU: 3 UID: 1000 PID: 3243376 Comm: fswarn\n  Call Trace:\n   get_tree_nodev+0x71/0xa0\n   ovl_get_tree+0x15/0x20 [overlay]\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. ovl_parse_param()\nalready spells a user namespace check this way for Opt_override_creds.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}