The nsenter --join-cgroup option opens the target cgroup.procs file as root and leaves that file descriptor open across later namespace and credential changes and across execve(). Because the kernel checks later cgroup migrations using the credentials from the original open, a program run in an attacker-controlled target can inherit root's ability to move host processes between cgroups. After a privileged operator uses --join-cgroup against that target, an unprivileged user can migrate and terminate unrelated root processes.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - The nsenter --join-cgroup option opens the target cgroup.procs file as root and leaves that file
    descriptor open across later namespace and credential changes and across execve(). Because the kernel
    checks later cgroup migrations using the credentials from the original open, a program run in an attacker-
    controlled target can inherit root's ability to move host processes between cgroups. After a privileged
    operator uses --join-cgroup against that target, an unprivileged user can migrate and terminate unrelated
    root processes. (CVE-2026-78408)

The remote SUSE Linux SLES16 / SLES_SAP16 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:23870-1 advisory.

    - CVE-2026-13595: heap use-after-free in `libblkid` nested partition probing (bsc#1269583).
    - CVE-2026-27456: TOCTOU in the mount program when setting up loop devices (bsc#1261606).
    - CVE-2026-53612: local privilege escalation via TOCTOU in mount(8) hook_owner.c chmod/chown     (bsc#1268886).
    - CVE-2026-53613: local privilege escalation via TOCTOU in mount(8) - Target Path Redirection     (bsc#1268886).
    - CVE-2026-53614: local privilege escalation via LIBMOUNT_FORCE_MOUNT2 Environment Variable -     nosuid/noexec       Bypass in SUID mount(8) (bsc#1268886).
    - CVE-2026-76642: failed external mount helper triggers privileged `X-mount` post-hooks, which enables     local privilege       escalation (bsc#1278349).
    - CVE-2026-78408: `nsenter --join-cgroup` leaks root `cgroup` migration authority, which allows for     migration or       termination of root processes (bsc#1278348).
    - CVE-2026-78410: restricted `bind` mounts do not pin the source, which allows for     `X-mount.owner`/`group`/`mode`       redirection (bsc#1278347).

    Changes for util-linux:

    - lib/fileutils: add ul_openat_resolve() openat2 wrapper (bsc#1275441)
    - lib/fileutils: fix RESOLVE_NO_SYMLINKS fallback value
    - lib/fileutils: fix unused parameter warnings without SYS_openat2
    - libmount: add missing fileutils.h include to hook_idmap.c
    - libmount: add mnt_open_tree() helper for safe tree opening
    - libmount: pin source path with openat2() for restricted users      (bsc#1275441, bsc#1278347, CVE-2026-78410)
    - libmount: restrict source path canonicalization for non-root      users (bsc#1275441, bsc#1278347, CVE-2026-78410)
    - libmount: skip post-mount hooks after failed mount helper      (bsc#1275441, bsc#1278349, CVE-2026-76642)
    - libmount: use USE_LIBMOUNT_MOUNTFD_SUPPORT for idmap hook
    - nsenter: close cgroup.procs fd after join to prevent authority      leak (bsc#1275441, bsc#1278348, CVE-2026-78408)
    - nsenter, unshare: add O_CLOEXEC to all open() calls (bsc#1275441,      bsc#1278348, CVE-2026-78408)
    - wall, write: sanitize hostname in banner header (bsc#1275441)
    - Add missing function. (bsc#1275441)
    - ipcutils: Prevent using uninitialized variable (bsc#1268886)
    - BREAKING CHANGE:
     Paths must always be canonicalized for unprivileged users to      ensure safe target resolution. X-mount.nocanonicalize is ignored      for them.
    - INCOMAPTIBLE CHANGE (linux < 6.15):
     X-mount.subdir: The safe detached subdirectory is no more      supported for unprivileged users for safety reasons.
    - liblastlog2: Wait on busy SQLite connections (bsc#1268886).
    - libmount: Fix subvolid buffer overflow in get_btrfs_fs_root      (bsc#1268886).
    - libblkid: Fix use-after-free in nested partition probing      (bsc#1269583, bsc#1268886, CVE-2026-13595)
    - libmount: fix SUID bypass via LIBMOUNT_FORCE_MOUNT2 and legacy      mount path (bsc#1268886, CVE-2026-53614, GHSA-67r7-8m5w-22wx).
    - fileutils: add ul_open_no_symlinks() needed by other patches      (bsc#1268886).
    - libmount: add fd_target to context for TOCTOU race condition      prevention (bsc#1268886, CVE-2026-53613, GHSA-8gj5-72r3-428g).
    - libmount: ignore X-mount.nocanonicalize for restricted users
    - libmount: use fd-based fchownat/chmod in hook_owner (bsc#1268886,      CVE-2026-53612, GHSA-g8wm-75wr-g2vh).
    - libmount: restrict X-mount.subdir for non-root (bsc#1268886).
    - libmount: use fd_target in hook_idmap for move_mount()
    - libmount: add mount ID verification and man page TOCTOU note
    - loopdev: use openat2(RESOLVE_NO_SYMLINKS) for backing file      (bsc#1268886#c2, bsc#1261606).
    - Ignore pam-config error that prevents update failure if common*      pam configuration is not symlink to common-*-pc (bsc#1270219).

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote openSUSE 16 host has packages installed that are affected by multiple vulnerabilities as referenced in the openSUSE-SU-2026:21905-1 advisory.

    - CVE-2026-13595: heap use-after-free in `libblkid` nested partition probing (bsc#1269583).
    - CVE-2026-27456: TOCTOU in the mount program when setting up loop devices (bsc#1261606).
    - CVE-2026-53612: local privilege escalation via TOCTOU in mount(8) hook_owner.c chmod/chown     (bsc#1268886).
    - CVE-2026-53613: local privilege escalation via TOCTOU in mount(8) - Target Path Redirection     (bsc#1268886).
    - CVE-2026-53614: local privilege escalation via LIBMOUNT_FORCE_MOUNT2 Environment Variable -     nosuid/noexec       Bypass in SUID mount(8) (bsc#1268886).
    - CVE-2026-76642: failed external mount helper triggers privileged `X-mount` post-hooks, which enables     local privilege       escalation (bsc#1278349).
    - CVE-2026-78408: `nsenter --join-cgroup` leaks root `cgroup` migration authority, which allows for     migration or       termination of root processes (bsc#1278348).
    - CVE-2026-78410: restricted `bind` mounts do not pin the source, which allows for     `X-mount.owner`/`group`/`mode`       redirection (bsc#1278347).

    Changes for util-linux:

    - lib/fileutils: add ul_openat_resolve() openat2 wrapper (bsc#1275441)
    - lib/fileutils: fix RESOLVE_NO_SYMLINKS fallback value
    - lib/fileutils: fix unused parameter warnings without SYS_openat2
    - libmount: add missing fileutils.h include to hook_idmap.c
    - libmount: add mnt_open_tree() helper for safe tree opening
    - libmount: pin source path with openat2() for restricted users      (bsc#1275441, bsc#1278347, CVE-2026-78410)
    - libmount: restrict source path canonicalization for non-root      users (bsc#1275441, bsc#1278347, CVE-2026-78410)
    - libmount: skip post-mount hooks after failed mount helper      (bsc#1275441, bsc#1278349, CVE-2026-76642)
    - libmount: use USE_LIBMOUNT_MOUNTFD_SUPPORT for idmap hook
    - nsenter: close cgroup.procs fd after join to prevent authority      leak (bsc#1275441, bsc#1278348, CVE-2026-78408)
    - nsenter, unshare: add O_CLOEXEC to all open() calls (bsc#1275441,      bsc#1278348, CVE-2026-78408)
    - wall, write: sanitize hostname in banner header (bsc#1275441)
    - Add missing function. (bsc#1275441)
    - ipcutils: Prevent using uninitialized variable (bsc#1268886)
    - BREAKING CHANGE:
     Paths must always be canonicalized for unprivileged users to      ensure safe target resolution. X-mount.nocanonicalize is ignored      for them.
    - INCOMAPTIBLE CHANGE (linux < 6.15):
     X-mount.subdir: The safe detached subdirectory is no more      supported for unprivileged users for safety reasons.
    - liblastlog2: Wait on busy SQLite connections (bsc#1268886).
    - libmount: Fix subvolid buffer overflow in get_btrfs_fs_root      (bsc#1268886).
    - libblkid: Fix use-after-free in nested partition probing      (bsc#1269583, bsc#1268886, CVE-2026-13595)
    - libmount: fix SUID bypass via LIBMOUNT_FORCE_MOUNT2 and legacy      mount path (bsc#1268886, CVE-2026-53614, GHSA-67r7-8m5w-22wx).
    - fileutils: add ul_open_no_symlinks() needed by other patches      (bsc#1268886).
    - libmount: add fd_target to context for TOCTOU race condition      prevention (bsc#1268886, CVE-2026-53613, GHSA-8gj5-72r3-428g).
    - libmount: ignore X-mount.nocanonicalize for restricted users
    - libmount: use fd-based fchownat/chmod in hook_owner (bsc#1268886,      CVE-2026-53612, GHSA-g8wm-75wr-g2vh).
    - libmount: restrict X-mount.subdir for non-root (bsc#1268886).
    - libmount: use fd_target in hook_idmap for move_mount()
    - libmount: add mount ID verification and man page TOCTOU note
    - loopdev: use openat2(RESOLVE_NO_SYMLINKS) for backing file      (bsc#1268886#c2, bsc#1261606).
    - Ignore pam-config error that prevents update failure if common*      pam configuration is not symlink to common-*-pc (bsc#1270219).

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The version of util-linux installed on the remote host is prior to 2.42.4. It is, therefore, affected by a vulnerability as referenced in the SSA:2026-264-01 advisory.

    New util-linux packages are available for Slackware 15.0 and -current to fix a security issue.

Tenable has extracted the preceding description block directly from the util-linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The version of util-linux installed on the remote host is prior to 2.42.3. It is, therefore, affected by multiple vulnerabilities as referenced in the SSA:2026-249-03 advisory.

    New util-linux packages are available for Slackware 15.0 and -current to fix security issues.

Tenable has extracted the preceding description block directly from the util-linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - The nsenter --join-cgroup option opens the target cgroup.procs file as root and leaves that file     descriptor open across later namespace and credential changes and across execve(). Because the kernel     checks later cgroup migrations using the credentials from the original open, a program run in an attacker-     controlled target can inherit root's ability to move host processes between cgroups. After a privileged     operator uses --join-cgroup against that target, an unprivileged user can migrate and terminate unrelated     root processes. (CVE-2026-78408)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Type	Severity
463591	Echo: util-linux: security update to 2.41.5-0+deb13u1+e2	Tenable Cloud Security	Echo Local Security Checks	Local	high
463591	Echo: util-linux: security update to 2.41.5-0+deb13u1+e2	Tenable Self-Hosted Container Security	Echo Local Security Checks	Local	high
350831	SUSE SLES16: lastlog2 / libblkid-devel / libblkid-devel-static / libblkid1 / etc (SUSE-SU-2026:23870-1)	Nessus	SuSE Local Security Checks	Local	high
350149	openSUSE 16: lastlog2 / libblkid-devel / libblkid-devel-static / libblkid1 / etc (openSUSE-SU-2026:21905-1)	Nessus	SuSE Local Security Checks	Local	high
348696	Slackware Linux 15.0 / current util-linux Vulnerability (SSA:2026-264-01)	Nessus	Slackware Local Security Checks	Local	high
343408	Slackware Linux 15.0 / current util-linux Multiple Vulnerabilities (SSA:2026-249-03)	Nessus	Slackware Local Security Checks	Local	high
342439	Linux Distros Unpatched Vulnerability : CVE-2026-78408	Nessus	Misc.	Local	high

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