Linux Distros Unpatched Vulnerability : CVE-2026-93800

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
##

include('compat.inc');

if (description)
{
  script_id(349802);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/09/24");

  script_cve_id("CVE-2026-93800");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-93800");

  script_set_attribute(attribute:"synopsis", value:
"The Linux/Unix host has one or more packages installed with a vulnerability that the vendor indicates will not be
patched.");
  script_set_attribute(attribute:"description", value:
"The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied
patch available.

  - btrfs: fix use-after-free on reloc root after error in insert_dirty_subvol() If during relocation we fail
    in insert_dirty_subvol() because btrfs_update_reloc_root() returned an error, we will leave a root's
    reloc_root field pointing to a reloc root that was freed instead of NULL, resulting later in a use-after-
    free, or double free attempt during unmount. The sequence of steps is this: 1) During relocation the call
    to btrfs_update_reloc_root() in insert_dirty_subvol() fails, so insert_dirty_subvol() returns the error to
    merge_reloc_root() without adding the root to the list rc->dirty_subvol_roots; 2) Then merge_reloc_root()
    aborts the current transaction because insert_dirty_subvol() returned an error; 3) Up the call chain,
    merge_reloc_roots() gets the error, adds the reloc root for root X to the local reloc_roots list and jumps
    to the 'out' label, where it calls free_reloc_roots() to free all the reloc roots in the local reloc_roots
    list. This frees the reloc root for root X; 4) We go up the call chain to relocate_block_group() which
    calls clean_dirty_subvols() to go over dirty roots and set their ->reloc_root field to NULL, but root X is
    not in the dirty_subvol_roots list, so its ->reloc_root still points to a reloc root; 5) Relocation
    finishes, with an error and a transaction abort, but the ->reloc_root field for root X still points to the
    reloc root that was freed in step 3; 6) When unmounting the fs we end up calling: btrfs_free_fs_roots()
    btrfs_drop_and_free_fs_root() --> calls btrfs_put_root() against root X's ->reloc_root which is not NULL
    and points to the already freed reloc root in step 4 above Resulting in a use-after-free to a double free
    attempt. Syzbot reported this with the following dmesg/syslog: [ 106.004389][ T5339] BTRFS error (device
    loop0 state A): Transaction aborted (error -5) [ 106.014266][ T5339] BTRFS: error (device loop0 state A)
    in merge_reloc_root:1655: errno=-5 IO failure [ 106.021891][ T1061] BTRFS error (device loop0 state A):
    error while writing out transaction: -5 [ 106.026964][ T1061] BTRFS warning (device loop0 state A):
    Skipping commit of aborted transaction. [ 106.033807][ T5340] BTRFS error (device loop0 state A): bdev
    /dev/loop0 errs: wr 3, rd 0, flush 0, corrupt 0, gen 0 [ 106.039265][ T1061] BTRFS: error (device loop0
    state A) in cleanup_transaction:2067: errno=-5 IO failure [ 106.044382][ T5339] BTRFS info (device loop0
    state EA): forced readonly [ 106.074329][ T5339] BTRFS: error (device loop0 state EA) in
    merge_reloc_roots:1887: errno=-5 IO failure [ 106.081004][ T5356] BTRFS info (device loop0 state EA):
    scrub: started on devid 1 [ 106.085611][ T5339] BTRFS info (device loop0 state EA): balance: ended with
    status: -30 [ 106.089517][ T5356] BTRFS info (device loop0 state EA): scrub: not finished on devid 1 with
    status: -30 [ 106.662365][ T5338] BTRFS info (device loop0 state EA): last unmount of filesystem
    3a375e4e-b156-4d76-a2ad-16e198ce1409 [ 106.682946][ T5338]
    ================================================================== [ 106.686574][ T5338] BUG: KASAN: slab-
    use-after-free in btrfs_put_root+0x2f/0x250 [ 106.690090][ T5338] Write of size 4 at addr ffff88803f978630
    by task syz.0.0/5338 [ 106.693173][ T5338] [ 106.694279][ T5338] CPU: 0 UID: 0 PID: 5338 Comm: syz.0.0 Not
    tainted syzkaller #0 PREEMPT(full) [ 106.694293][ T5338] Hardware name: QEMU Standard PC (Q35 + ICH9,
    2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 106.694300][ T5338] Call Trace: [ 106.694308][ T5338]
    <TASK> [ 106.694314][ T5338] dump_stack_lvl+0xe8/0x150 [ 106.694331][ T5338]
    print_address_description+0x55/0x1e0 [ 106.694343][ T5338] ? btrfs_put_root+0x2f/0x250 [ 106.694358][
    T5338] print_report+0x58/0x70 [ 106. ---truncated--- (CVE-2026-93800)

Note that Nessus relies on the presence of the package as reported by the vendor.");
  script_set_attribute(attribute:"see_also", value:"https://security-tracker.debian.org/tracker/CVE-2026-93800");
  script_set_attribute(attribute:"solution", value:
"There is no known solution at this time.");
  script_set_attribute(attribute:"agent", value:"unix");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:U/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:U/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-93800");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");
  script_set_attribute(attribute:"vendor_unpatched", value:"true");

  script_set_attribute(attribute:"vuln_publication_date", value:"2026/09/24");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/09/24");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:12.0");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:13.0");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:linux");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Misc.");

  script_copyright(english:"This script is Copyright (C) 2026 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info2.nasl", "set_linux_os_id.nasl");
  script_require_keys("Host/cpu", "Host/local_checks_enabled", "global_settings/vendor_unpatched", "Host/OS/identifier");
  script_require_ports("Host/OS/Debian Linux-12", "Host/OS/Debian Linux-13");

  exit(0);
}

if (!get_kb_item("global_settings/vendor_unpatched")) exit(0, "Unpatched Vulnerabilities Detection not active.");
if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
if (empty_or_null(get_one_kb_item("Host/Debian/dpkg-l"))) audit(AUDIT_PACKAGE_LIST_MISSING);

include('linux_unpatched.inc');

var distro_constraints_array = {
  "Debian Linux-12": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "12",
        "pkgs": [
          {"reference": "btrfs-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "cdrom-core-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "ext4-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "fat-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "isofs-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "jfs-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "kernel-image-6.1.0-50-alpha-generic-di"},
          {"reference": "linux-doc"},
          {"reference": "linux-doc-6.1"},
          {"reference": "linux-headers-6.1.0"},
          {"reference": "linux-source"},
          {"reference": "linux-source-6.1"},
          {"reference": "linux-support-6.1.0"},
          {"reference": "loop-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "nic-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "nic-shared-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "nic-wireless-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "pata-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "ppp-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "scsi-core-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "scsi-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "scsi-nic-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "serial-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "usb-serial-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "xfs-modules-6.1.0-50-alpha-generic-di"}
        ]
      }
    ]
  },
  "Debian Linux-13": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "13",
        "pkgs": [
          {"reference": "bpftool"},
          {"reference": "hyperv-daemons"},
          {"reference": "intel-sdsi"},
          {"reference": "libcpupower-dev"},
          {"reference": "libcpupower1"},
          {"reference": "linux-bpf-dev"},
          {"reference": "linux-config-6.12"},
          {"reference": "linux-cpupower"},
          {"reference": "linux-doc"},
          {"reference": "linux-doc-6.12"},
          {"reference": "linux-headers-4kc-malta"},
          {"reference": "linux-headers-5kc-malta"},
          {"reference": "linux-headers-6.12.107+deb13-4kc-malta"},
          {"reference": "linux-headers-6.12.107+deb13-5kc-malta"},
          {"reference": "linux-headers-6.12.107+deb13-alpha-generic"},
          {"reference": "linux-headers-6.12.107+deb13-alpha-smp"},
          {"reference": "linux-headers-6.12.107+deb13-amd64"},
          {"reference": "linux-headers-6.12.107+deb13-arm64"},
          {"reference": "linux-headers-6.12.107+deb13-arm64-16k"},
          {"reference": "linux-headers-6.12.107+deb13-armmp"},
          {"reference": "linux-headers-6.12.107+deb13-armmp-lpae"},
          {"reference": "linux-headers-6.12.107+deb13-cloud-amd64"},
          {"reference": "linux-headers-6.12.107+deb13-cloud-arm64"},
          {"reference": "linux-headers-6.12.107+deb13-common"},
          {"reference": "linux-headers-6.12.107+deb13-common-rt"},
          {"reference": "linux-headers-6.12.107+deb13-loong64"},
          {"reference": "linux-headers-6.12.107+deb13-loongson-3"},
          {"reference": "linux-headers-6.12.107+deb13-m68k"},
          {"reference": "linux-headers-6.12.107+deb13-mips32r2eb"},
          {"reference": "linux-headers-6.12.107+deb13-mips32r2el"},
          {"reference": "linux-headers-6.12.107+deb13-mips64r2eb"}
        ]
      }
    ]
  }
};

var distro_constraints_values = linux_unpatched::get_distro_constraints(distro_constraints_arr:distro_constraints_array);
if (empty_or_null(distro_constraints_values)) audit(AUDIT_HOST_NOT, 'affected');

var third_party_support = get_kb_item('Host/OS/extended-third-party');
if (!empty_or_null(third_party_support)) {
    var third_party_vendors = distro_constraints_values['third_party'];
    if (!empty_or_null(third_party_vendors)) {
        var vendor;
        foreach vendor (third_party_vendors) {
            if (vendor == third_party_support) exit(0, 'A third party management patch is available for this vulnerability from ' + vendor + '.\n');
        }
    }
}

var report = linux_unpatched::check_unpatched_constraints(distro_constraints_values:distro_constraints_values);

if (!empty_or_null(report))
{
  security_report_v4(
      port       : 0,
      severity   : SECURITY_WARNING,
      extra      : report
  );
  exit(0);
}
else
{
  audit(AUDIT_HOST_NOT, 'affected');
}