Linux Distros Unpatched Vulnerability : CVE-2026-99033

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

include('compat.inc');

if (description)
{
  script_id(371591);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/10/23");

  script_cve_id("CVE-2026-99033");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-99033");

  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.

  - net/packet: guard the ll header push in packet_rcv_spkt() packet_rcv_spkt() restores the link layer header
    with skb_push(skb, skb->data - skb_mac_header(skb)); That subtraction is only meaningful when the device
    actually has a link layer header. packet_rcv() and tpacket_rcv() both wrap it in dev_has_header(), which
    is also the predicate the block comment at the top of the file states the restore in terms of;
    packet_rcv_spkt() does not. commit d549699048b4 (net/packet: fix packet receive on L3 devices without
    visible hard header) introduced the helper and changed the two call sites, and this one stayed behind. A
    device without a visible ll header can leave skb->mac_header at the 0xFFFF sentinel that __alloc_skb()
    initialises it to. A CAN skb does: init_can_skb() sets pkt_type and ip_summed but does not reset the
    headers, and commit 9f10374bb024 (can: remove private CAN skb headroom infrastructure) dropped the
    skb_reset_*_header() calls that used to be there. skb_mac_header() is then 0xFFFF, the length becomes a
    large negative number and skb_push() reports it through skb_under_panic() -- from softirq context, so it
    is a full system panic even with panic_on_oops=0: skbuff: skb_under_panic: text:ffffffff8bd21bc1
    len:-65455 put:-65471 head:... data:... tail:0x50 end:0x180 dev:can0 kernel BUG at net/core/skbuff.c:214!
    RIP: 0010:skb_panic+0x50/0x60 Call Trace: <IRQ> skb_push+0x38/0x40 packet_rcv_spkt+0xe1/0x170
    __netif_receive_skb_core.constprop.0+0x7e8/0xd30 ... Kernel panic - not syncing: Fatal exception in
    interrupt The socket type is reachable: packet_create() accepts SOCK_PACKET alongside SOCK_RAW and
    SOCK_DGRAM behind the same CAP_NET_RAW check, and neither the socket length nor a capability check keeps
    it away from a CAN interface. The missing skb_reset_*_header() calls in init_can_skb() are a regression in
    their own right and are being fixed separately, but a packet socket should not turn a link layer that did
    not initialise its mac header into a kernel panic. Guard the push the way the other two receive paths do.
    Tested on v7.3-rc5 under QEMU with a slcan device on a pty, which is the driver RX path: vcan does not
    reproduce it, because can_send() resets the headers on the way out. One SOCK_PACKET socket bound to can0
    and one frame written into the line discipline panics an unpatched kernel with the trace above; the same
    image with this patch prints no panic and powers off normally. Both kernels are this tree, defconfig plus
    CONFIG_CAN_SLCAN=y, differing only in this hunk. (CVE-2026-99033)

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-2026-99033");
  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-2026-99033");

  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:"2026/10/23");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/10/23");

  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:"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");

  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"}
        ]
      }
    ]
  }
};

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');
}