Linux Distros Unpatched Vulnerability : CVE-2026-53034

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

include('compat.inc');

if (description)
{
  script_id(322624);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/06/25");

  script_cve_id("CVE-2026-53034");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-53034");

  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, sockmap: Fix af_unix null-ptr-deref in proto update unix_stream_connect() sets sk_state
    (`WRITE_ONCE(sk->sk_state, TCP_ESTABLISHED)`) _before_ it assigns a peer (`unix_peer(sk) = newsk`).
    sk_state == TCP_ESTABLISHED makes sock_map_sk_state_allowed() believe that socket is properly set up,
    which would include having a defined peer. IOW, there's a window when unix_stream_bpf_update_proto() can
    be called on socket which still has unix_peer(sk) == NULL. CPU0 bpf CPU1 connect -------- ------------
    WRITE_ONCE(sk->sk_state, TCP_ESTABLISHED) sock_map_sk_state_allowed(sk) ... sk_pair = unix_peer(sk)
    sock_hold(sk_pair) sock_hold(newsk) smp_mb__after_atomic() unix_peer(sk) = newsk BUG: kernel NULL pointer
    dereference, address: 0000000000000080 RIP: 0010:unix_stream_bpf_update_proto+0xa0/0x1b0 Call Trace:
    sock_map_link+0x564/0x8b0 sock_map_update_common+0x6e/0x340 sock_map_update_elem_sys+0x17d/0x240
    __sys_bpf+0x26db/0x3250 __x64_sys_bpf+0x21/0x30 do_syscall_64+0x6b/0x3a0
    entry_SYSCALL_64_after_hwframe+0x76/0x7e Initial idea was to move peer assignment _before_ the sk_state
    update[1], but that involved an additional memory barrier, and changing the hot path was rejected. Then a
    NULL check during proto update in unix_stream_bpf_update_proto() was considered[2], but the follow-up
    discussion[3] focused on the root cause, i.e. sockmap update taking a wrong lock. Or, more specifically,
    missing unix_state_lock()[4]. In the end it was concluded that teaching sockmap about the af_unix locking
    would be unnecessarily complex[5]. Complexity aside, since BPF_PROG_TYPE_SCHED_CLS and
    BPF_PROG_TYPE_SCHED_ACT are allowed to update sockmaps, sock_map_update_elem() taking the unix lock, as it
    is currently implemented in unix_state_lock(): spin_lock(&unix_sk(s)->lock), would be problematic.
    unix_state_lock() taken in a process context, followed by a softirq-context TC BPF program attempting to
    take the same spinlock -- deadlock[6]. This way we circled back to the peer check idea[2]. [1]:
    https://lore.kernel.org/netdev/[email protected]/ [2]:
    https://lore.kernel.org/netdev/[email protected]/ [3]:
    https://lore.kernel.org/netdev/[email protected]/ [4]:
    https://lore.kernel.org/netdev/CAAVpQUA+8GL_j63CaKb8hbxoL21izD58yr1NvhOhU=j+35+3og@mail.gmail.com/ [5]:
    https://lore.kernel.org/bpf/CAAVpQUAHijOMext28Gi10dSLuMzGYh+jK61Ujn+fZ-wvcODR2A@mail.gmail.com/ [6]:
    https://lore.kernel.org/bpf/[email protected]/ Summary of scenarios where
    af_unix/stream connect() may race a sockmap update: 1. connect() vs. bpf(BPF_MAP_UPDATE_ELEM), i.e.
    sock_map_update_elem_sys() Implemented NULL check is sufficient. Once assigned, socket peer won't be
    released until socket fd is released. And that's not an issue because sock_map_update_elem_sys() bumps fd
    refcnf. 2. connect() vs BPF program doing update Update restricted per verifier.c:may_update_sockmap() to
    BPF_PROG_TYPE_TRACING/BPF_TRACE_ITER BPF_PROG_TYPE_SOCK_OPS (bpf_sock_map_update() only)
    BPF_PROG_TYPE_SOCKET_FILTER BPF_PROG_TYPE_SCHED_CLS BPF_PROG_TYPE_SCHED_ACT BPF_PROG_TYPE_XDP
    BPF_PROG_TYPE_SK_REUSEPORT BPF_PROG_TYPE_FLOW_DISSECTOR BPF_PROG_TYPE_SK_LOOKUP Plus one more race to
    consider: CPU0 bpf CPU1 connect -------- ------------ WRITE_ONCE(sk->sk_state, TCP_ESTABLISHED)
    sock_map_sk_state_allowed(sk) sock_hold(newsk) smp_mb__after_atomic() ---truncated--- (CVE-2026-53034)

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-2026-53034");
  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-2026-53034");

  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:"2026/06/24");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/06/25");

  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-6.1.0-47-alpha-generic-di"},
          {"reference": "cdrom-core-modules-6.1.0-47-alpha-generic-di"},
          {"reference": "ext4-modules-6.1.0-47-alpha-generic-di"},
          {"reference": "fat-modules-6.1.0-47-alpha-generic-di"},
          {"reference": "isofs-modules-6.1.0-47-alpha-generic-di"},
          {"reference": "jfs-modules-6.1.0-47-alpha-generic-di"},
          {"reference": "kernel-image-6.1.0-47-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-6.1.0-47-alpha-generic-di"},
          {"reference": "nic-modules-6.1.0-47-alpha-generic-di"},
          {"reference": "nic-shared-modules-6.1.0-47-alpha-generic-di"},
          {"reference": "nic-wireless-modules-6.1.0-47-alpha-generic-di"},
          {"reference": "pata-modules-6.1.0-47-alpha-generic-di"},
          {"reference": "ppp-modules-6.1.0-47-alpha-generic-di"},
          {"reference": "scsi-core-modules-6.1.0-47-alpha-generic-di"},
          {"reference": "scsi-modules-6.1.0-47-alpha-generic-di"},
          {"reference": "scsi-nic-modules-6.1.0-47-alpha-generic-di"},
          {"reference": "serial-modules-6.1.0-47-alpha-generic-di"},
          {"reference": "usb-serial-modules-6.1.0-47-alpha-generic-di"},
          {"reference": "xfs-modules-6.1.0-47-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 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');
}