AlmaLinux 9.6 [TuxCare] Security Update: libpng / libpng-devel / libpng-static / libpng-tools Multiple Vulnerabilities (ALMALINUX9.6:CLSA-2026:1778054892)

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

include('compat.inc');

if (description)
{
  script_id(362143);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/10/01");

  script_cve_id("CVE-2026-33416", "CVE-2026-33636");
  script_xref(name:"CLSA", value:"2026:1778054892");

  script_name(english:"AlmaLinux 9.6 [TuxCare] Security Update: libpng / libpng-devel / libpng-static / libpng-tools Multiple Vulnerabilities (ALMALINUX9.6:CLSA-2026:1778054892)");

  script_set_attribute(attribute:"synopsis", value:
"The AlmaLinux host is missing one or more security updates.");
  script_set_attribute(attribute:"description", value:
"The AlmaLinux 9.6 host has packages installed that are affected by multiple vulnerabilities as referenced in the TuxCare
ALMALINUX9.6:CLSA-2026:1778054892 advisory.

  - LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable
    Network Graphics) raster image files. In versions 1.2.1 through 1.6.55, `png_set_tRNS` and `png_set_PLTE`
    each alias a heap-allocated buffer between `png_struct` and `png_info`, sharing a single allocation across
    two structs with independent lifetimes. The `trans_alpha` aliasing has been present since at least libpng
    1.0, and the `palette` aliasing since at least 1.2.1. Both affect all prior release lines `png_set_tRNS`
    sets `png_ptr->trans_alpha = info_ptr->trans_alpha` (256-byte buffer) and `png_set_PLTE` sets
    `info_ptr->palette = png_ptr->palette` (768-byte buffer). In both cases, calling `png_free_data` (with
    `PNG_FREE_TRNS` or `PNG_FREE_PLTE`) frees the buffer through `info_ptr` while the corresponding `png_ptr`
    pointer remains dangling. Subsequent row-transform functions dereference and, in some code paths, write to
    the freed memory. A second call to `png_set_tRNS` or `png_set_PLTE` has the same effect, because both
    functions call `png_free_data` internally before reallocating the `info_ptr` buffer. Version 1.6.56 fixes
    the issue. (CVE-2026-33416)

  - LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable
    Network Graphics) raster image files. In versions 1.6.36 through 1.6.55, an out-of-bounds read and write
    exists in libpng's ARM/AArch64 Neon-optimized palette expansion path. When expanding 8-bit paletted rows
    to RGB or RGBA, the Neon loop processes a final partial chunk without verifying that enough input pixels
    remain. Because the implementation works backward from the end of the row, the final iteration
    dereferences pointers before the start of the row buffer (OOB read) and writes expanded pixel data to the
    same underflowed positions (OOB write). This is reachable via normal decoding of attacker-controlled PNG
    input if Neon is enabled. Version 1.6.56 fixes the issue. (CVE-2026-33636)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version
number.");
  # https://security.tuxcare.com/csaf/v2/els_os/tuxcare9.6esu/advisories/2026/clsa-2026_1778054892.json
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?7fe4ad92");
  script_set_attribute(attribute:"see_also", value:"https://cve.tuxcare.com/els/releases/CLSA-2026:1778054892");
  script_set_attribute(attribute:"solution", value:
"Update the affected packages based on the guidance in TuxCare advisory ALMALINUX9.6:CLSA-2026:1778054892.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:POC/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-33636");

  script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"true");
  script_set_attribute(attribute:"vendor_severity", value:"Important");

  script_set_attribute(attribute:"vuln_publication_date", value:"2026/03/10");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/05/06");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/10/01");

  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:"Alma 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/OS/extended-third-party", "Host/local_checks_enabled", "Host/AlmaLinux/release", "Host/AlmaLinux/rpm-list", "Host/cpu");

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

var third_party_support = get_kb_item('Host/OS/extended-third-party');
if (empty_or_null(third_party_support) || third_party_support != 'TuxCare') exit(0, 'TuxCare support not enabled.');

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) || 'AlmaLinux' >!< os_product) audit(AUDIT_OS_NOT, 'AlmaLinux');
var os_version = get_kb_item('installed_os/local/SSH/0/version');
if (isnull(os_version)) audit(AUDIT_UNKNOWN_APP_VER, 'AlmaLinux');
if (! preg(pattern:"^9.6([^0-9]|$)", string:os_version)) audit(AUDIT_OS_NOT, 'AlmaLinux 9.6', 'AlmaLinux ' + os_version);

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

var cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if (cpu !~ "^i[3-6]86$" && 'x86_64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'AlmaLinux', cpu);


var constraints = [
  {
    'release': '9',
    'sp': '6',
    'pkgs': [
      {'reference':'libpng-1.6.37-12.el9_6.tuxcare.els7', 'sp':'6', 'cpu':'i686', 'el_string':'el9_6', 'rpm_spec_vers_cmp':TRUE, 'epoch':'2'},
      {'reference':'libpng-1.6.37-12.el9_6.tuxcare.els7', 'sp':'6', 'cpu':'x86_64', 'el_string':'el9_6', 'rpm_spec_vers_cmp':TRUE, 'epoch':'2'},
      {'reference':'libpng-devel-1.6.37-12.el9_6.tuxcare.els7', 'sp':'6', 'cpu':'i686', 'el_string':'el9_6', 'rpm_spec_vers_cmp':TRUE, 'epoch':'2'},
      {'reference':'libpng-devel-1.6.37-12.el9_6.tuxcare.els7', 'sp':'6', 'cpu':'x86_64', 'el_string':'el9_6', 'rpm_spec_vers_cmp':TRUE, 'epoch':'2'},
      {'reference':'libpng-static-1.6.37-12.el9_6.tuxcare.els7', 'sp':'6', 'cpu':'x86_64', 'el_string':'el9_6', 'rpm_spec_vers_cmp':TRUE, 'epoch':'2'},
      {'reference':'libpng-tools-1.6.37-12.el9_6.tuxcare.els7', 'sp':'6', 'cpu':'x86_64', 'el_string':'el9_6', 'rpm_spec_vers_cmp':TRUE, 'epoch':'2'}
    ]
  }
];

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_HOLE,
      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, 'libpng / libpng-devel / libpng-static / libpng-tools');
}