AlmaLinux 9.6 [TuxCare] Security Update: libevent / libevent-devel / libevent-doc Multiple Vulnerabilities (ALMALINUX9.6:CLSA-2026:1790587734)

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

include('compat.inc');

if (description)
{
  script_id(361749);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/10/01");

  script_cve_id(
    "CVE-2026-63379",
    "CVE-2026-63381",
    "CVE-2026-63382",
    "CVE-2026-63383",
    "CVE-2026-63384",
    "CVE-2026-63385",
    "CVE-2026-63387",
    "CVE-2026-63388"
  );
  script_xref(name:"CLSA", value:"2026:1790587734");

  script_name(english:"AlmaLinux 9.6 [TuxCare] Security Update: libevent / libevent-devel / libevent-doc Multiple Vulnerabilities (ALMALINUX9.6:CLSA-2026:1790587734)");

  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-2026:1790587734 advisory.

  - Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent processes chunked
    HTTP trailers in http.c through evhttp_read_trailer and merges them into request headers. The fix
    introduces evhttp_parse_headers_impl_ and a temporary trailer header list. An unauthenticated remote
    attacker can place security-sensitive fields in trailers so that an upstream proxy and the libevent
    application interpret different effective headers, enabling header smuggling, authorization bypass, proxy-
    header spoofing, or cache poisoning. The fix parses trailers into a temporary header list and discards
    them instead of merging them into req->input_headers. This issue is fixed in versions 2.1.13 and
    2.2.2-alpha. (CVE-2026-63379)

  - Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has a use-after-free
    in buffer.c when evbuffer_add_buffer_reference processes an output buffer whose out_total_len is zero.
    evbuffer_free_all_chains frees the initial empty chain without resetting outbuf->first, outbuf->last, or
    outbuf->last_with_datap, and APPEND_CHAIN_MULTICAST subsequently dereferences the dangling chain pointer.
    A caller that can drive this buffer state can cause memory corruption or a process crash. This issue is
    fixed in versions 2.1.13 and 2.2.2-alpha. (CVE-2026-63381)

  - Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, the libevent evhttp parser in
    http.c inconsistently handles duplicate Transfer-Encoding headers, comma-separated Transfer-Encoding
    values, and bare line feeds in chunked framing. evhttp_find_header can select only the first header,
    evhttp_check_transfer_encoding_ was absent so the previous whole-string comparison fails to recognize
    valid lists ending in chunked, and evhttp_handle_chunked_read uses EVBUFFER_EOL_CRLF rather than
    EVBUFFER_EOL_CRLF_STRICT, accepting bare LF chunk terminators. When libevent is deployed behind a proxy
    that frames the same request differently, an unauthenticated remote attacker can desynchronize request
    boundaries and smuggle a second request, potentially bypassing access controls or poisoning caches. This
    issue is fixed in versions 2.1.13 and 2.2.2-alpha. (CVE-2026-63382)

  - Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent can read beyond a
    contiguous evbuffer region in event_tagging.c when decode_tag_internal requests at most five bytes from
    evbuffer_pullup but iterates using the full logical buffer length. A fragmented evbuffer containing a six-
    byte malformed tag can therefore advance past the pullup window and trigger an out-of-bounds read, which
    can crash a process that decodes attacker-controlled tagged RPC data. This issue is fixed in versions
    2.1.13 and 2.2.2-alpha. (CVE-2026-63383)

  - Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has an incorrect
    integer conversion in event_tagging.c when evtag_unmarshal_header uses evtag_decode_int to decode an
    attacker-controlled uint32 payload length and returns it as a signed int. Values above INT_MAX become
    negative or truncated, and evtag_unmarshal_string can use the converted value in allocation sizing,
    producing a wrapped large allocation request and denial of service. This issue is fixed in versions 2.1.13
    and 2.2.2-alpha. (CVE-2026-63384)

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_1790587734.json
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?6bd79523");
  script_set_attribute(attribute:"see_also", value:"https://cve.tuxcare.com/els/releases/CLSA-2026:1790587734");
  script_set_attribute(attribute:"solution", value:
"Update the affected packages based on the guidance in TuxCare advisory ALMALINUX9.6:CLSA-2026:1790587734.");
  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:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/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:O/RC:C");
  script_set_attribute(attribute:"cvss4_vector", value:"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:L/SI:L/SA:N");
  script_set_attribute(attribute:"cvss4_threat_vector", value:"CVSS:4.0/E:U");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-63387");
  script_set_attribute(attribute:"cvss3_score_source", value:"CVE-2026-63388");
  script_set_attribute(attribute:"cvss4_score_source", value:"CVE-2026-63385");

  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_severity", value:"Important");

  script_set_attribute(attribute:"vuln_publication_date", value:"2026/08/20");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/09/28");
  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 ('aarch64' >!< cpu && cpu !~ "^i[3-6]86$" && 'x86_64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'AlmaLinux', cpu);


var constraints = [
  {
    'release': '9',
    'sp': '6',
    'pkgs': [
      {'reference':'libevent-2.1.12-8.el9_6.tuxcare.els2', 'sp':'6', 'cpu':'aarch64', 'el_string':'el9_6', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libevent-2.1.12-8.el9_6.tuxcare.els2', 'sp':'6', 'cpu':'i686', 'el_string':'el9_6', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libevent-2.1.12-8.el9_6.tuxcare.els2', 'sp':'6', 'cpu':'x86_64', 'el_string':'el9_6', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libevent-devel-2.1.12-8.el9_6.tuxcare.els2', 'sp':'6', 'cpu':'aarch64', 'el_string':'el9_6', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libevent-devel-2.1.12-8.el9_6.tuxcare.els2', 'sp':'6', 'cpu':'i686', 'el_string':'el9_6', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libevent-devel-2.1.12-8.el9_6.tuxcare.els2', 'sp':'6', 'cpu':'x86_64', 'el_string':'el9_6', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libevent-doc-2.1.12-8.el9_6.tuxcare.els2', 'sp':'6', 'el_string':'el9_6', '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_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, 'libevent / libevent-devel / libevent-doc');
}