Linux Distros Unpatched Vulnerability : CVE-2026-98869

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

include('compat.inc');

if (description)
{
  script_id(370051);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/10/21");

  script_cve_id("CVE-2026-98869");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-98869");

  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.

  - bpf: Infer zext_dst based on static register liveness analysis As reported in the thread [1], the
    verifier's 32-bit operations zero extension logic is broken. This logic is responsible for correct
    semantics of 32-bit operations on s390 architecture. According to BPF semantics, operation `w1 += 1` is
    supposed to zero extend the upper half of the register `r1`. On s390 the JIT relies on the verifier
    emitting explicit zero extension before such operations. The verifier attempts to minimize the amount of
    zero extensions inserted by tracking whether upper halves of the 64-bit registers are ever used.
    Previously such tracking worked as follows: - bpf_reg_state->subreg_def field was set by do_check_insn()
    for each operation defining lower but not the upper halves of the register. - Whenever an operation
    reading the whole register was verified, the verifier checked register's subreg_def and set
    bpf_insn_aux_data->zext_dst flag as true via a call to mark_insn_zext() function. - After the verification
    was complete, a special pass bpf_opt_subreg_zext_lo32_rnd_hi32() extended 32-bit operations with
    bpf_insn_aux_data->zext_dst set as true by adding explicit zero extension. Note that the logic above
    relies on bpf_reg_state->subreg_def, which is a property of a current verifier state. Before the commit
    [2] two additional steps happened: - The verifier tracked upper and lower register halves' liveness as
    flags REG_LIVE_READ{32,64} in bpf_reg_state->live. - The function propagate_liveness() called
    mark_insn_zext() in order to transfer the knowledge about which registers have their upper halves alive
    (and thus might require zero extension). The commit [2] removed the two steps described above, hence
    making possible a situation like below: - The register's upper half is set and is used on some
    verification path P1 and the register happens not to be marked as precise. - The checkpoint C is created
    while processing some instruction between register initialization and usage. - On some other verification
    path P2 the register's upper half is not initialized and that path ends hitting the checkpoint C. - In
    such a case the register's initialization on path P2 would lack zext_dst mark, making it possible for the
    program to inject an arbitrary value in the register's upper half. This commit replaces subreg_def based
    logic with computing zext_dst statically, as a part of the bpf_compute_live_registers() analysis: - The
    analysis now tracks usage of upper and lower halves of the registers separately. - If some instruction
    defines a 32-bit subregister, but not the whole register, *and* the upper half of the register is alive
    after that instruction, the instruction is marked as zext_dst. There is one notable drop in precision:
    whenever a BPF subprogram is called, all 64 bits of parameter registers are presumed to be used. The
    assumption is that such a drop in precision would not inflict a noticeable performance penalty. [1]
    https://lore.kernel.org/bpf/CAGKGUv=sOuqQtA1Ub-5JXfA4FPosJFYKAQE4B79cK+P1erxqtg@mail.gmail.com/ [2] commit
    107e16979905 (bpf: disable and remove registers chain based liveness) (CVE-2026-98869)

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-2026-98869");
  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-2026-98869");

  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:"2026/10/21");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/10/21");

  script_set_attribute(attribute:"plugin_type", value:"local");
  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-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-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-7.2.11+deb14-alpha-generic"},
          {"reference": "linux-base-7.2.11+deb14-amd64"},
          {"reference": "linux-base-7.2.11+deb14-arm64"},
          {"reference": "linux-base-7.2.11+deb14-arm64-16k"},
          {"reference": "linux-base-7.2.11+deb14-armmp"},
          {"reference": "linux-base-7.2.11+deb14-armmp-lpae"},
          {"reference": "linux-base-7.2.11+deb14-cloud-amd64"},
          {"reference": "linux-base-7.2.11+deb14-cloud-arm64"},
          {"reference": "linux-base-7.2.11+deb14-loong64"},
          {"reference": "linux-base-7.2.11+deb14-m68k"},
          {"reference": "linux-base-7.2.11+deb14-parisc"},
          {"reference": "linux-base-7.2.11+deb14-parisc64"},
          {"reference": "linux-base-7.2.11+deb14-powerpc"},
          {"reference": "linux-base-7.2.11+deb14-powerpc64"},
          {"reference": "linux-base-7.2.11+deb14-powerpc64-64k"},
          {"reference": "linux-base-7.2.11+deb14-powerpc64le"},
          {"reference": "linux-base-7.2.11+deb14-powerpc64le-64k"},
          {"reference": "linux-base-7.2.11+deb14-riscv64"},
          {"reference": "linux-base-7.2.11+deb14-rt-amd64"},
          {"reference": "linux-base-7.2.11+deb14-rt-arm64"},
          {"reference": "linux-base-7.2.11+deb14-s390x"},
          {"reference": "linux-base-7.2.11+deb14-sh7751r"},
          {"reference": "linux-base-7.2.11+deb14-sparc64"},
          {"reference": "linux-base-7.2.11+deb14-test"},
          {"reference": "linux-base-alpha-generic"},
          {"reference": "linux-base-armmp"},
          {"reference": "linux-base-armmp-lpae"},
          {"reference": "linux-base-loong64"}
        ]
      }
    ]
  }
};

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');
}