Linux Distros Unpatched Vulnerability : CVE-2021-46955

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

include('compat.inc');

if (description)
{
  script_id(250032);
  script_version("1.10");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/05/21");

  script_cve_id("CVE-2021-46955");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2021-46955");

  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.

  - In the Linux kernel, the following vulnerability has been resolved: openvswitch: fix stack OOB read while
    fragmenting IPv4 packets running openvswitch on kernels built with KASAN, it's possible to see the
    following splat while testing fragmentation of IPv4 packets: BUG: KASAN: stack-out-of-bounds in
    ip_do_fragment+0x1b03/0x1f60 Read of size 1 at addr ffff888112fc713c by task handler2/1367 CPU: 0 PID:
    1367 Comm: handler2 Not tainted 5.12.0-rc6+ #418 Hardware name: Red Hat KVM, BIOS
    1.11.1-4.module+el8.1.0+4066+0f1aadab 04/01/2014 Call Trace: dump_stack+0x92/0xc1
    print_address_description.constprop.7+0x1a/0x150 kasan_report.cold.13+0x7f/0x111
    ip_do_fragment+0x1b03/0x1f60 ovs_fragment+0x5bf/0x840 [openvswitch] do_execute_actions+0x1bd5/0x2400
    [openvswitch] ovs_execute_actions+0xc8/0x3d0 [openvswitch] ovs_packet_cmd_execute+0xa39/0x1150
    [openvswitch] genl_family_rcv_msg_doit.isra.15+0x227/0x2d0 genl_rcv_msg+0x287/0x490
    netlink_rcv_skb+0x120/0x380 genl_rcv+0x24/0x40 netlink_unicast+0x439/0x630 netlink_sendmsg+0x719/0xbf0
    sock_sendmsg+0xe2/0x110 ____sys_sendmsg+0x5ba/0x890 ___sys_sendmsg+0xe9/0x160 __sys_sendmsg+0xd3/0x170
    do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f957079db07 Code: c3 66 90
    41 54 41 89 d4 55 48 89 f5 53 89 fb 48 83 ec 10 e8 eb ec ff ff 44 89 e2 48 89 ee 89 df 41 89 c0 b8 2e 00
    00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 48 89 44 24 08 e8 24 ed ff ff 48 RSP: 002b:00007f956ce35a50
    EFLAGS: 00000293 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 0000000000000019 RCX:
    00007f957079db07 RDX: 0000000000000000 RSI: 00007f956ce35ae0 RDI: 0000000000000019 RBP: 00007f956ce35ae0
    R08: 0000000000000000 R09: 00007f9558006730 R10: 0000000000000000 R11: 0000000000000293 R12:
    0000000000000000 R13: 00007f956ce37308 R14: 00007f956ce35f80 R15: 00007f956ce35ae0 The buggy address
    belongs to the page: page:00000000af2a1d93 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0
    pfn:0x112fc7 flags: 0x17ffffc0000000() raw: 0017ffffc0000000 0000000000000000 dead000000000122
    0000000000000000 raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 page dumped
    because: kasan: bad access detected addr ffff888112fc713c is located in stack of task handler2/1367 at
    offset 180 in frame: ovs_fragment+0x0/0x840 [openvswitch] this frame has 2 objects: [32, 144) 'ovs_dst'
    [192, 424) 'ovs_rt' Memory state around the buggy address: ffff888112fc7000: f3 00 00 00 00 00 00 00 00 00
    00 00 00 00 00 00 ffff888112fc7080: 00 f1 f1 f1 f1 00 00 00 00 00 00 00 00 00 00 00 >ffff888112fc7100: 00
    00 00 f2 f2 f2 f2 f2 f2 00 00 00 00 00 00 00 ^ ffff888112fc7180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    00 00 ffff888112fc7200: 00 00 00 00 00 00 f2 f2 f2 00 00 00 00 00 00 00 for IPv4 packets, ovs_fragment()
    uses a temporary struct dst_entry. Then, in the following call graph: ip_do_fragment() ip_skb_dst_mtu()
    ip_dst_mtu_maybe_forward() ip_mtu_locked() the pointer to struct dst_entry is used as pointer to struct
    rtable: this turns the access to struct members like rt_mtu_locked into an OOB read in the stack. Fix this
    changing the temporary variable used for IPv4 packets in ovs_fragment(), similarly to what is done for
    IPv6 few lines below. (CVE-2021-46955)

Note that Nessus relies on the presence of the package as reported by the vendor.");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/CVE-2021-46955");
  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:L/AC:M/Au:N/C:P/I:N/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:U/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/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-2021-46955");

  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:"2022/01/28");
  script_set_attribute(attribute:"plugin_publication_date", value:"2025/08/15");

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

  script_copyright(english:"This script is Copyright (C) 2025-2026 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/Ubuntu Linux-16.04", "Host/OS/Ubuntu Linux-18.04", "Host/OS/Ubuntu Linux-20.04", "Host/OS/Ubuntu Linux-22.04", "Host/OS/Ubuntu Linux-24.04");

  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 = {
  "Ubuntu Linux-16.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "16.04",
        "pkgs": [
          {"reference": "linux-hwe-edge"}
        ]
      }
    ]
  },
  "Ubuntu Linux-18.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "18.04",
        "pkgs": [
          {"reference": "linux-aws-5.0"},
          {"reference": "linux-aws-5.3"},
          {"reference": "linux-azure-5.3"},
          {"reference": "linux-azure-cloud-tools-4.15.0"},
          {"reference": "linux-azure-edge"},
          {"reference": "linux-azure-headers-4.15.0"},
          {"reference": "linux-azure-tools-4.15.0"},
          {"reference": "linux-cloud-tools-4.15.0"},
          {"reference": "linux-gcp-5.3"},
          {"reference": "linux-gcp-headers-4.15.0"},
          {"reference": "linux-gcp-tools-4.15.0"},
          {"reference": "linux-gke-4.15"},
          {"reference": "linux-gke-5.4"},
          {"reference": "linux-gkeop-5.4"},
          {"reference": "linux-headers-4.15.0"},
          {"reference": "linux-hwe"},
          {"reference": "linux-hwe-edge"},
          {"reference": "linux-image-4.15.0"},
          {"reference": "linux-image-unsigned-4.15.0"},
          {"reference": "linux-modules-4.15.0"},
          {"reference": "linux-modules-extra-4.15.0"},
          {"reference": "linux-oem-headers-4.15.0"},
          {"reference": "linux-oem-tools-4.15.0"},
          {"reference": "linux-oracle-5.0"},
          {"reference": "linux-oracle-5.3"},
          {"reference": "linux-tools-4.15.0"},
          {"reference": "linux-udebs-azure"},
          {"reference": "linux-udebs-oem"}
        ]
      }
    ]
  },
  "Ubuntu Linux-20.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "20.04",
        "pkgs": [
          {"reference": "linux-aws-5.11"},
          {"reference": "linux-aws-5.13"},
          {"reference": "linux-aws-5.8"},
          {"reference": "linux-azure-5.11"},
          {"reference": "linux-azure-5.13"},
          {"reference": "linux-azure-5.8"},
          {"reference": "linux-azure-fde"},
          {"reference": "linux-buildinfo-5.4.0"},
          {"reference": "linux-buildinfo-5.6.0"},
          {"reference": "linux-cloud-tools-5.4.0"},
          {"reference": "linux-cloud-tools-5.6.0"},
          {"reference": "linux-gcp-5.11"},
          {"reference": "linux-gcp-5.13"},
          {"reference": "linux-gcp-5.8"},
          {"reference": "linux-gke"},
          {"reference": "linux-gke-5.15"},
          {"reference": "linux-headers-5.4.0"},
          {"reference": "linux-headers-5.6.0"},
          {"reference": "linux-hwe-5.11"},
          {"reference": "linux-hwe-5.13"},
          {"reference": "linux-hwe-5.8"},
          {"reference": "linux-image-5.4.0"},
          {"reference": "linux-image-unsigned-5.6.0"},
          {"reference": "linux-intel-5.13"},
          {"reference": "linux-libc-dev"},
          {"reference": "linux-modules-5.4.0"},
          {"reference": "linux-modules-5.6.0"},
          {"reference": "linux-modules-extra-5.4.0"},
          {"reference": "linux-modules-extra-5.6.0"},
          {"reference": "linux-oem-5.10"},
          {"reference": "linux-oem-5.13"},
          {"reference": "linux-oem-5.14"},
          {"reference": "linux-oem-5.6-headers-5.6.0"},
          {"reference": "linux-oem-5.6-tools-5.6.0"},
          {"reference": "linux-oem-5.6-tools-common"},
          {"reference": "linux-oem-5.6-tools-host"},
          {"reference": "linux-oracle-5.11"},
          {"reference": "linux-oracle-5.13"},
          {"reference": "linux-oracle-5.8"},
          {"reference": "linux-raspi2"},
          {"reference": "linux-riscv-5.11"},
          {"reference": "linux-riscv-5.8"},
          {"reference": "linux-riscv-headers-5.4.0"},
          {"reference": "linux-riscv-tools-5.4.0"},
          {"reference": "linux-tools-5.4.0"},
          {"reference": "linux-tools-5.6.0"},
          {"reference": "linux-udebs-generic"},
          {"reference": "linux-udebs-oem"}
        ]
      }
    ]
  },
  "Ubuntu Linux-22.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "22.04",
        "pkgs": [
          {"reference": "linux-allwinner-5.19"},
          {"reference": "linux-aws-5.19"},
          {"reference": "linux-aws-6.2"},
          {"reference": "linux-azure-5.19"},
          {"reference": "linux-azure-6.2"},
          {"reference": "linux-azure-fde-5.19"},
          {"reference": "linux-azure-fde-6.2"},
          {"reference": "linux-buildinfo-5.15.0"},
          {"reference": "linux-buildinfo-5.17.0"},
          {"reference": "linux-cloud-tools-5.15.0"},
          {"reference": "linux-cloud-tools-5.17.0"},
          {"reference": "linux-gcp-5.19"},
          {"reference": "linux-gcp-6.2"},
          {"reference": "linux-headers-5.15.0"},
          {"reference": "linux-headers-5.17.0"},
          {"reference": "linux-hwe-5.19"},
          {"reference": "linux-hwe-6.2"},
          {"reference": "linux-image-5.15.0"},
          {"reference": "linux-image-unsigned-5.17.0"},
          {"reference": "linux-intel-iot-realtime"},
          {"reference": "linux-lowlatency-hwe-5.19"},
          {"reference": "linux-lowlatency-hwe-6.2"},
          {"reference": "linux-modules-5.15.0"},
          {"reference": "linux-modules-5.17.0"},
          {"reference": "linux-modules-extra-5.15.0"},
          {"reference": "linux-modules-extra-5.17.0"},
          {"reference": "linux-nvidia-6.2"},
          {"reference": "linux-oem-5.17-headers-5.17.0"},
          {"reference": "linux-oem-5.17-tools-5.17.0"},
          {"reference": "linux-oem-5.17-tools-host"},
          {"reference": "linux-oem-6.0"},
          {"reference": "linux-oem-6.1"},
          {"reference": "linux-realtime"},
          {"reference": "linux-riscv-5.19"},
          {"reference": "linux-riscv-headers-5.15.0"},
          {"reference": "linux-riscv-tools-5.15.0"},
          {"reference": "linux-starfive-5.19"},
          {"reference": "linux-starfive-6.2"},
          {"reference": "linux-tools-5.15.0"},
          {"reference": "linux-tools-5.17.0"}
        ]
      }
    ]
  },
  "Ubuntu Linux-24.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "24.04",
        "pkgs": [
          {"reference": "linux-raspi-realtime"}
        ]
      }
    ]
  }
};

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 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');
}