Linux Distros Unpatched Vulnerability : CVE-2026-63825

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

include('compat.inc');

if (description)
{
  script_id(327843);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/07/19");

  script_cve_id("CVE-2026-63825");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-63825");

  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.

  - gcov: use atomic counter updates to fix concurrent access crashes GCC's GCOV instrumentation can merge
    global branch counters with loop induction variables as an optimization. In inflate_fast(), the inner copy
    loops get transformed so that the GCOV counter value is loaded multiple times to compute the loop base
    address, start index, and end bound. Since GCOV counters are global (not per-CPU), concurrent execution on
    different CPUs causes the counter to change between loads, producing inconsistent values and out-of-bounds
    memory writes. The crash manifests during IPComp (IP Payload Compression) processing when inflate_fast()
    runs concurrently on multiple CPUs: BUG: unable to handle page fault for address: ffffd0a3c0902ffa RIP:
    inflate_fast+1431 Call Trace: zlib_inflate __deflate_decompress crypto_comp_decompress ipcomp_decompress
    [xfrm_ipcomp] ipcomp_input [xfrm_ipcomp] xfrm_input At the crash point, the compiler generated three loads
    from the same global GCOV counter (__gcov0.inflate_fast+216) to compute base, start, and end for an
    indexed loop. Another CPU modified the counter between loads, making the values inconsistent - the write
    went 3.4 MB past a 65 KB buffer. Add -fprofile-update=prefer-atomic to CFLAGS_GCOV at the global level in
    the top-level Makefile, guarded by a try-run compile test. The test compiles a minimal program with and
    without -fprofile-update=prefer-atomic using the full KBUILD_CFLAGS, then compares undefined symbols in
    the resulting object files. If prefer-atomic introduces new undefined references (such as
    __atomic_fetch_add_8 on i386 or __aarch64_ldadd8_relax on arm64 with outline-atomics), the flag is not
    added -- the kernel does not link against libatomic. On architectures where GCC inlines 64-bit atomic
    counter updates (x86_64, s390, ...) the test passes and the flag is enabled, preventing the compiler from
    merging counters with loop induction variables and fixing the observed concurrent-access crash. On
    architectures where the flag would introduce libatomic dependencies, it is silently omitted and behaviour
    is no worse than before this patch. Move the CFLAGS_GCOV block from its original position (before the arch
    Makefile include) to after the core KBUILD_CFLAGS assignments but before the scripts/Makefile.gcc-plugins
    include. This placement ensures the try-run test sees arch-specific flags (-m32, -march=, -mno-outline-
    atomics) while avoiding GCC plugin flags (-fplugin=) that would break the test on clean builds when plugin
    shared objects do not yet exist. (CVE-2026-63825)

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-2026-63825");
  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-2026-63825");

  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:"2026/07/19");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/07/19");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:11.0");
  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:"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-11", "Host/OS/Debian Linux-12", "Host/OS/Debian Linux-13");

  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-11": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "11",
        "pkgs": [
          {"reference": "bpftool"},
          {"reference": "btrfs-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "cdrom-core-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "hyperv-daemons"},
          {"reference": "kernel-image-5.10.0-32-alpha-generic-di"},
          {"reference": "libcpupower-dev"},
          {"reference": "libcpupower1"},
          {"reference": "linux-bootwrapper-5.10.0"},
          {"reference": "linux-config-5.10"},
          {"reference": "linux-cpupower"},
          {"reference": "linux-doc"},
          {"reference": "linux-doc-5.10"},
          {"reference": "linux-headers-5.10.0"},
          {"reference": "linux-kbuild-5.10"},
          {"reference": "linux-libc-dev"},
          {"reference": "linux-perf"},
          {"reference": "linux-perf-5.10"},
          {"reference": "linux-source"},
          {"reference": "linux-source-5.10"},
          {"reference": "linux-support-5.10.0"},
          {"reference": "loop-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "nic-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "nic-shared-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "nic-wireless-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "pata-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "ppp-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "scsi-core-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "scsi-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "scsi-nic-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "serial-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "usb-serial-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "usbip"}
        ]
      }
    ]
  },
  "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');
}