{"apiVersion":"1.0","identifier":"CVE-2026-74619","description":"In the Linux kernel, the following vulnerability has been resolved: ovl: don-t warn when the mount is completed from another user namespace fsopen() records the caller-s user namespace in fc->user_ns and hands back an ordinary file descriptor. Nothing ties the task that calls fsconfig(FSCONFIG_CMD_CREATE) to the task that created the context. The fd is inherited across fork() and exec() and it can be passed over a unix socket. Completing a context from another user namespace is allowed on purpose. vfs_cmd_create() authorizes the create with mount_capable(), which for FS_USERNS_MOUNT checks ns_capable(fc->user_ns, CAP_SYS_ADMIN), and that succeeds for a task holding CAP_SYS_ADMIN in an ancestor of fc->user_ns. So an unprivileged task can reach the WARN_ON() in ovl_fill_super(): create a user and a mount namespace in a child, call fsopen(-overlay-) there, send the fscontext fd to the parent and let the parent issue FSCONFIG_CMD_CREATE. Both namespaces come from a plain unshare(1) and no capability is needed anywhere: WARNING: fs/overlayfs/super.c:1551 at ovl_fill_super+0x7b9/0x1e20 [overlay] CPU: 3 UID: 1000 PID: 3243376 Comm: fswarn Call Trace: get_tree_nodev+0x71/0xa0 ovl_get_tree+0x15/0x20 [overlay] vfs_get_tree+0x2a/0x100 vfs_cmd_create+0x60/0xf0 __do_sys_fsconfig+0x4b2/0x500 The child needs the mount namespace because fsopen() itself gates on may_mount(), which asks for CAP_SYS_ADMIN in the user namespace owning the caller-s mount namespace. fsconfig() doesn-t repeat that check. It is a WARN_ON() and not a WARN_ON_ONCE(), so the condition can be raised in a loop to taint the kernel and flood the log, and it panics a kernel booted with panic_on_warn. Keep refusing the mount and stop warning about it. ovl_parse_param() already spells a user namespace check this way for Opt_override_creds.","publishedAt":"2026-08-22T16:16:34","lastModifiedAt":"2026-08-22T16:16:34","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-74619","cvssScore":null,"cvssVector":"Pending","epssProbability":0.00168,"riskScore":0,"affectedProduct":"Linux kernel","affectedVersions":"unknown","vulnerabilityType":"Kernel","operatingSystems":[],"links":{"self":"https://www.redsauce.net/api/cves/CVE-2026-74619","webPages":{"es":"https://www.redsauce.net/es/cves/CVE-2026-74619","en":"https://www.redsauce.net/en/cves/CVE-2026-74619","fr":"https://www.redsauce.net/fr/cves/CVE-2026-74619","pt":"https://www.redsauce.net/pt/cves/CVE-2026-74619","de":"https://www.redsauce.net/de/cves/CVE-2026-74619","sk":"https://www.redsauce.net/sk/cves/CVE-2026-74619","el":"https://www.redsauce.net/el/cves/CVE-2026-74619"},"source":"https://nvd.nist.gov/vuln/detail/CVE-2026-74619"}}