Linux Distros Unpatched Vulnerability : CVE-2026-80840

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

include('compat.inc');

if (description)
{
  script_id(342967);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/09/04");

  script_cve_id("CVE-2026-80840");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-80840");

  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.

  - ipv6: seg6: clear IPv4 control block on IPIP decapsulation End.DX4 and End.DT4 decapsulate an IPv4 packet
    through decap_and_validate() and send it directly to IPv4 routing. The inner packet therefore bypasses
    ip_rcv_core(), which normally clears IPCB before IPv4 interprets skb->cb. The skb instead retains IP6CB
    data from the outer packet. IP6CB and IPCB use the same skb->cb storage, so IP6CB(skb)->lastopt overlaps
    IPCB(skb)->opt.optlen and srr, while IP6CB(skb)->nhoff overlaps rr and ts. The sender can make the stale
    optlen byte nonzero with a valid outer extension-header chain. The reproducers put an eight-byte
    Destination Options header immediately after the 40-byte IPv6 header and before the Segment Routing
    Header. ipv6_destopt_rcv() records the sender-controlled Destination Options offset in both lastopt and
    nhoff, setting them to 40. On the reproduced little-endian x86-64 kernel, IPv4 therefore sees optlen = 40
    and rr = 40. Both tcp_v4_save_options() and __ip_options_echo() skip option copying when optlen is zero.
    Here optlen is 40, so the TCP SYN path allocates room for 40 bytes of option data and calls
    __ip_options_echo(). The stale rr value makes that function read inner packet byte 41 as the Record Route
    option length. The reproducers set that sender-controlled byte to 255, so __ip_options_echo() copies 255
    bytes into the 40-byte option-data area. Separate End.DX4 and End.DT4 reproducers on the unpatched
    v7.2-rc5 kernel both produced: BUG: KASAN: slab-out-of-bounds in __ip_options_echo() Write of size 255 The
    relevant End.DX4 call path is: __ip_options_echo tcp_v4_route_req tcp_conn_request tcp_v4_conn_request
    tcp_rcv_state_process tcp_v4_do_rcv tcp_v4_rcv ip_protocol_deliver_rcu ip_local_deliver_finish
    ip_local_deliver input_action_end_dx4_finish input_action_end_dx4 The relevant End.DT4 call path is:
    __ip_options_echo tcp_v4_route_req tcp_conn_request tcp_v4_conn_request tcp_rcv_state_process
    tcp_v4_do_rcv tcp_v4_rcv ip_protocol_deliver_rcu ip_local_deliver_finish ip_local_deliver
    input_action_end_dt4 tcp_v4_save_options() is inlined into the tcp_v4_route_req() path, so it does not
    appear as a separate frame. When decap_and_validate() handles IPPROTO_IPIP, save the ingress interface
    from IP6CB, clear IPCB, and restore the saved value. Doing this in the common decapsulation path covers
    End.DX4, End.DT4, and End.DT46's IPv4 arm. Use IP6CB(skb)->iif rather than skb->skb_iif. These actions run
    after l3mdev processing, which can replace skb_iif with the L3 master; IP6CB iif still records the
    receiving interface set at IPv6 ingress. (CVE-2026-80840)

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-2026-80840");
  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-2026-80840");

  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:"2026/09/04");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/09/04");

  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:"cpe:/o:debian:debian_linux:14.0");
  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", "Host/OS/Debian Linux-14");

  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-14": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "14",
        "pkgs": [
          {"reference": "bpftool"},
          {"reference": "hyperv-daemons"},
          {"reference": "intel-sdsi"},
          {"reference": "libcpupower-dev"},
          {"reference": "libcpupower1"},
          {"reference": "linux-base-7.1.12+deb14-alpha-generic"},
          {"reference": "linux-base-7.1.12+deb14-alpha-smp"},
          {"reference": "linux-base-7.1.12+deb14-amd64"},
          {"reference": "linux-base-7.1.12+deb14-arm64"},
          {"reference": "linux-base-7.1.12+deb14-arm64-16k"},
          {"reference": "linux-base-7.1.12+deb14-armmp"},
          {"reference": "linux-base-7.1.12+deb14-armmp-lpae"},
          {"reference": "linux-base-7.1.12+deb14-cloud-amd64"},
          {"reference": "linux-base-7.1.12+deb14-cloud-arm64"},
          {"reference": "linux-base-7.1.12+deb14-loong64"},
          {"reference": "linux-base-7.1.12+deb14-m68k"},
          {"reference": "linux-base-7.1.12+deb14-parisc"},
          {"reference": "linux-base-7.1.12+deb14-parisc64"},
          {"reference": "linux-base-7.1.12+deb14-powerpc"},
          {"reference": "linux-base-7.1.12+deb14-powerpc-smp"},
          {"reference": "linux-base-7.1.12+deb14-powerpc64"},
          {"reference": "linux-base-7.1.12+deb14-powerpc64-64k"},
          {"reference": "linux-base-7.1.12+deb14-powerpc64le"},
          {"reference": "linux-base-7.1.12+deb14-powerpc64le-64k"},
          {"reference": "linux-base-7.1.12+deb14-riscv64"},
          {"reference": "linux-base-7.1.12+deb14-rt-amd64"},
          {"reference": "linux-base-7.1.12+deb14-rt-arm64"},
          {"reference": "linux-base-7.1.12+deb14-s390x"},
          {"reference": "linux-base-7.1.12+deb14-sh7751r"},
          {"reference": "linux-base-7.1.12+deb14-sparc64"},
          {"reference": "linux-base-7.1.12+deb14-sparc64-smp"}
        ]
      }
    ]
  },
  "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-6.12.94+deb13-4kc-malta"},
          {"reference": "linux-headers-6.12.94+deb13-5kc-malta"},
          {"reference": "linux-headers-6.12.94+deb13-alpha-generic"},
          {"reference": "linux-headers-6.12.94+deb13-alpha-smp"},
          {"reference": "linux-headers-6.12.94+deb13-amd64"},
          {"reference": "linux-headers-6.12.94+deb13-arm64"},
          {"reference": "linux-headers-6.12.94+deb13-arm64-16k"},
          {"reference": "linux-headers-6.12.94+deb13-armmp"},
          {"reference": "linux-headers-6.12.94+deb13-armmp-lpae"},
          {"reference": "linux-headers-6.12.94+deb13-cloud-amd64"},
          {"reference": "linux-headers-6.12.94+deb13-cloud-arm64"},
          {"reference": "linux-headers-6.12.94+deb13-common"},
          {"reference": "linux-headers-6.12.94+deb13-common-rt"},
          {"reference": "linux-headers-6.12.94+deb13-loong64"},
          {"reference": "linux-headers-6.12.94+deb13-loongson-3"},
          {"reference": "linux-headers-6.12.94+deb13-m68k"},
          {"reference": "linux-headers-6.12.94+deb13-mips32r2eb"},
          {"reference": "linux-headers-6.12.94+deb13-mips32r2el"},
          {"reference": "linux-headers-6.12.94+deb13-mips64r2eb"},
          {"reference": "linux-headers-6.12.94+deb13-mips64r2el"}
        ]
      }
    ]
  }
};

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');
}