CVE-2026-74619 (GCVE-0-2026-74619)

Vulnerability from cvelistv5 – Published: 2026-08-22 15:32 – Updated: 2026-08-22 15:32
VLAI
Title
ovl: don't warn when the mount is completed from another user namespace
Summary
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.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 1784fbc2ed9c888ea4e895f30a53207ed7ee8208 , < 513478092966dc9818d96dd2b3ed613fd2f6e30e (git)
Affected: 1784fbc2ed9c888ea4e895f30a53207ed7ee8208 , < 494346f2aab2489d379d43ff614aea447cf4e94d (git)
Affected: 1784fbc2ed9c888ea4e895f30a53207ed7ee8208 , < be161fa31e3e9cc828a3c1bd935edca461e8a7a1 (git)
Affected: 1784fbc2ed9c888ea4e895f30a53207ed7ee8208 , < 42d99fcd8006007e2f708bede6789f37f3910b30 (git)
Affected: 1784fbc2ed9c888ea4e895f30a53207ed7ee8208 , < 63981fc786daaa626cb14d9be1406f674d79f98f (git)
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Linux Linux Affected: 6.5
Unaffected: 0 , < 6.5 (semver)
Unaffected: 6.6.152 , ≤ 6.6.* (semver)
Unaffected: 6.12.104 , ≤ 6.12.* (semver)
Unaffected: 6.18.45 , ≤ 6.18.* (semver)
Unaffected: 7.1.9 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\novl: don\u0027t warn when the mount is completed from another user namespace\n\nfsopen() records the caller\u0027s user namespace in fc-\u003euser_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-\u003euser_ns, CAP_SYS_ADMIN), and that\nsucceeds for a task holding CAP_SYS_ADMIN in an ancestor of fc-\u003euser_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\u0027s mount namespace. fsconfig() doesn\u0027t 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."
        }
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      "providerMetadata": {
        "dateUpdated": "2026-08-22T15:32:03.511Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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    "dateReserved": "2026-08-15T05:44:03.921Z",
    "dateUpdated": "2026-08-22T15:32:03.511Z",
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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-\u003euser_ns, CAP_SYS_ADMIN), and that\\nsucceeds for a task holding CAP_SYS_ADMIN in an ancestor of fc-\u003euser_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\u0027s mount namespace. fsconfig() doesn\u0027t 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.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/overlayfs/super.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"1784fbc2ed9c888ea4e895f30a53207ed7ee8208\",\"lessThan\":\"513478092966dc9818d96dd2b3ed613fd2f6e30e\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1784fbc2ed9c888ea4e895f30a53207ed7ee8208\",\"lessThan\":\"494346f2aab2489d379d43ff614aea447cf4e94d\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1784fbc2ed9c888ea4e895f30a53207ed7ee8208\",\"lessThan\":\"be161fa31e3e9cc828a3c1bd935edca461e8a7a1\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1784fbc2ed9c888ea4e895f30a53207ed7ee8208\",\"lessThan\":\"42d99fcd8006007e2f708bede6789f37f3910b30\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1784fbc2ed9c888ea4e895f30a53207ed7ee8208\",\"lessThan\":\"63981fc786daaa626cb14d9be1406f674d79f98f\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/overlayfs/super.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.5\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.5\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.152\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.104\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.45\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.9\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/42d99fcd8006007e2f708bede6789f37f3910b30\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/494346f2aab2489d379d43ff614aea447cf4e94d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/513478092966dc9818d96dd2b3ed613fd2f6e30e\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/63981fc786daaa626cb14d9be1406f674d79f98f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/be161fa31e3e9cc828a3c1bd935edca461e8a7a1\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-24T14:36:11+00:00",
      "cve": "CVE-2026-74619",
      "id": "CVE-2026-74619",
      "initial_release_date": "2026-08-22T00:00:00+00:00",
      "product_status:known_affected": "184",
      "product_status:known_not_affected": "90",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ovl: don\u0027t warn when the mount is completed from another user namespace",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74619.json",
      "version": "3"
    }
  }
}



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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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