Vulnerabilities > CVE-2017-8923 - Out-of-bounds Write vulnerability in PHP

047910
CVSS 7.5 - HIGH
Attack vector
NETWORK
Attack complexity
LOW
Privileges required
NONE
Confidentiality impact
PARTIAL
Integrity impact
PARTIAL
Availability impact
PARTIAL
network
low complexity
php
CWE-787
nessus

Summary

The zend_string_extend function in Zend/zend_string.h in PHP through 7.1.5 does not prevent changes to string objects that result in a negative length, which allows remote attackers to cause a denial of service (application crash) or possibly have unspecified other impact by leveraging a script's use of .= with a long string.

Common Weakness Enumeration (CWE)

Nessus

  • NASL familyCGI abuses
    NASL idPHP_7_0_19.NASL
    descriptionAccording to its banner, the version of PHP running on the remote web server is 7.0.x prior to 7.0.19. It is, therefore, affected by the following vulnerabilities : - A memory allocation issue exists in the zend_string_extend() function in file Zend/zend_string.h when concatenating strings due to a failure to prevent changes to string objects that result in a negative length. An unauthenticated, remote attacker can exploit this to cause a denial of service condition or possibly other unspecified impact. (CVE-2017-8923) - A memory allocation issue exists in the i_zval_ptr_dtor() function in Zend/zend_variables.h when allocating large amounts of memory. An unauthenticated, remote attacker can exploit this, via crafted operations on array data structures, to cause a denial of service condition. (CVE-2017-9119)
    last seen2020-06-01
    modified2020-06-02
    plugin id100420
    published2017-05-25
    reporterThis script is Copyright (C) 2017-2018 Tenable Network Security, Inc.
    sourcehttps://www.tenable.com/plugins/nessus/100420
    titlePHP 7.0.x < 7.0.19 Multiple Vulnerabilities
    code
    #
    # (C) Tenable Network Security, Inc.
    #
    
    include("compat.inc");
    
    if (description)
    {
      script_id(100420);
      script_version("1.5");
      script_cvs_date("Date: 2018/07/24 18:56:10");
    
      script_cve_id(
        "CVE-2017-8923",
        "CVE-2017-9119"
      );
      script_bugtraq_id(
        98518,
        98596
      );
    
      script_name(english:"PHP 7.0.x < 7.0.19 Multiple Vulnerabilities");
      script_summary(english:"Checks the version of PHP.");
    
      script_set_attribute(attribute:"synopsis", value:
    "The version of PHP running on the remote web server is affected by
    multiple vulnerabilities.");
      script_set_attribute(attribute:"description", value:
    "According to its banner, the version of PHP running on the remote web
    server is 7.0.x prior to 7.0.19. It is, therefore, affected by the
    following vulnerabilities :
    
      - A memory allocation issue exists in the
        zend_string_extend() function in file Zend/zend_string.h
        when concatenating strings due to a failure to prevent
        changes to string objects that result in a negative
        length. An unauthenticated, remote attacker can exploit
        this to cause a denial of service condition or possibly
        other unspecified impact. (CVE-2017-8923)
    
      - A memory allocation issue exists in the
        i_zval_ptr_dtor() function in Zend/zend_variables.h when
        allocating large amounts of memory. An unauthenticated,
        remote attacker can exploit this, via crafted operations
        on array data structures, to cause a denial of service
        condition. (CVE-2017-9119)");
      script_set_attribute(attribute:"see_also", value:"http://php.net/ChangeLog-7.php#7.0.19");
      script_set_attribute(attribute:"solution", value:
    "Upgrade to PHP version 7.0.19 or later.");
      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:OF/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:O/RC:C");
      script_set_attribute(attribute:"exploitability_ease", value:"No exploit is required");
      script_set_attribute(attribute:"exploit_available", value:"false");
    
      script_set_attribute(attribute:"vuln_publication_date", value:"2016/09/20");
      script_set_attribute(attribute:"patch_publication_date", value:"2017/05/11");
      script_set_attribute(attribute:"plugin_publication_date", value:"2017/05/25");
    
      script_set_attribute(attribute:"plugin_type", value:"remote");
      script_set_attribute(attribute:"cpe", value:"cpe:/a:php:php");
      script_end_attributes();
    
      script_category(ACT_GATHER_INFO);
      script_family(english:"CGI abuses");
    
      script_copyright(english:"This script is Copyright (C) 2017-2018 Tenable Network Security, Inc.");
    
      script_dependencies("php_version.nasl");
      script_require_keys("www/PHP");
      script_require_ports("Services/www", 80);
    
      exit(0);
    }
    
    include("audit.inc");
    include("global_settings.inc");
    include("misc_func.inc");
    include("http.inc");
    include("webapp_func.inc");
    
    port = get_http_port(default:80, php:TRUE);
    
    php = get_php_from_kb(
      port : port,
      exit_on_fail : TRUE
    );
    
    version = php["ver"];
    source = php["src"];
    
    backported = get_kb_item('www/php/'+port+'/'+version+'/backported');
    
    if (report_paranoia < 2 && backported)
      audit(AUDIT_BACKPORT_SERVICE, port, "PHP "+version+" install");
    
    # Check that it is the correct version of PHP
    if (version =~ "^7(\.0)?$") audit(AUDIT_VER_NOT_GRANULAR, "PHP", port, version);
    if (version !~ "^7\.0\.") audit(AUDIT_NOT_DETECT, "PHP version 7.0.x", port);
    
    fix = "7.0.19";
    if (ver_compare(ver:version, fix:fix, strict:FALSE) < 0)
    {
      report =
        '\n  Version source    : ' + source +
        '\n  Installed version : ' + version +
        '\n  Fixed version     : ' + fix +
        '\n';
      security_report_v4(port:port, extra:report, severity:SECURITY_HOLE);
    }
    else audit(AUDIT_LISTEN_NOT_VULN, "PHP", port, version);
    
    
  • NASL familyCGI abuses
    NASL idPHP_7_1_5.NASL
    descriptionAccording to its banner, the version of PHP running on the remote web server is 7.1.x prior to 7.1.5. It is, therefore, affected by the following vulnerabilities : - A memory allocation issue exists in the zend_string_extend() function in file Zend/zend_string.h when concatenating strings due to a failure to prevent changes to string objects that result in a negative length. An unauthenticated, remote attacker can exploit this to cause a denial of service condition or possibly other unspecified impact. (CVE-2017-8923) - A memory allocation issue exists in the i_zval_ptr_dtor() function in Zend/zend_variables.h when allocating large amounts of memory. An unauthenticated, remote attacker can exploit this, via crafted operations on array data structures, to cause a denial of service condition. (CVE-2017-9119)
    last seen2020-06-01
    modified2020-06-02
    plugin id100421
    published2017-05-25
    reporterThis script is Copyright (C) 2017-2018 Tenable Network Security, Inc.
    sourcehttps://www.tenable.com/plugins/nessus/100421
    titlePHP 7.1.x < 7.1.5 Multiple Vulnerabilities
    code
    #
    # (C) Tenable Network Security, Inc.
    #
    
    include("compat.inc");
    
    if (description)
    {
      script_id(100421);
      script_version("1.5");
      script_cvs_date("Date: 2018/07/24 18:56:10");
    
      script_cve_id(
        "CVE-2017-8923",
        "CVE-2017-9119"
      );
      script_bugtraq_id(
        98518,
        98596
      );
    
      script_name(english:"PHP 7.1.x < 7.1.5 Multiple Vulnerabilities");
      script_summary(english:"Checks the version of PHP.");
    
      script_set_attribute(attribute:"synopsis", value:
    "The version of PHP running on the remote web server is affected by
    multiple vulnerabilities.");
      script_set_attribute(attribute:"description", value:
    "According to its banner, the version of PHP running on the remote web
    server is 7.1.x prior to 7.1.5. It is, therefore, affected by the
    following vulnerabilities :
    
      - A memory allocation issue exists in the
        zend_string_extend() function in file Zend/zend_string.h
        when concatenating strings due to a failure to prevent
        changes to string objects that result in a negative
        length. An unauthenticated, remote attacker can exploit
        this to cause a denial of service condition or possibly
        other unspecified impact. (CVE-2017-8923)
    
      - A memory allocation issue exists in the
        i_zval_ptr_dtor() function in Zend/zend_variables.h when
        allocating large amounts of memory. An unauthenticated,
        remote attacker can exploit this, via crafted operations
        on array data structures, to cause a denial of service
        condition. (CVE-2017-9119)");
      script_set_attribute(attribute:"see_also", value:"http://php.net/ChangeLog-7.php#7.1.5");
      script_set_attribute(attribute:"solution", value:
    "Upgrade to PHP version 7.1.5 or later.");
      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:OF/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:O/RC:C");
      script_set_attribute(attribute:"exploitability_ease", value:"No exploit is required");
      script_set_attribute(attribute:"exploit_available", value:"false");
    
      script_set_attribute(attribute:"vuln_publication_date", value:"2016/09/20");
      script_set_attribute(attribute:"patch_publication_date", value:"2017/05/11");
      script_set_attribute(attribute:"plugin_publication_date", value:"2017/05/25");
    
      script_set_attribute(attribute:"plugin_type", value:"remote");
      script_set_attribute(attribute:"cpe", value:"cpe:/a:php:php");
      script_end_attributes();
    
      script_category(ACT_GATHER_INFO);
      script_family(english:"CGI abuses");
    
      script_copyright(english:"This script is Copyright (C) 2017-2018 Tenable Network Security, Inc.");
    
      script_dependencies("php_version.nasl");
      script_require_keys("www/PHP");
      script_require_ports("Services/www", 80);
    
      exit(0);
    }
    
    include("audit.inc");
    include("global_settings.inc");
    include("misc_func.inc");
    include("http.inc");
    include("webapp_func.inc");
    
    port = get_http_port(default:80, php:TRUE);
    
    php = get_php_from_kb(
      port : port,
      exit_on_fail : TRUE
    );
    
    version = php["ver"];
    source = php["src"];
    
    backported = get_kb_item('www/php/'+port+'/'+version+'/backported');
    
    if (report_paranoia < 2 && backported)
      audit(AUDIT_BACKPORT_SERVICE, port, "PHP "+version+" install");
    
    # Check that it is the correct version of PHP
    if (version =~ "^7(\.1)?$") audit(AUDIT_VER_NOT_GRANULAR, "PHP", port, version);
    if (version !~ "^7\.1\.") audit(AUDIT_NOT_DETECT, "PHP version 7.1.x", port);
    
    fix = "7.1.5";
    if (ver_compare(ver:version, fix:fix, strict:FALSE) < 0)
    {
      report =
        '\n  Version source    : ' + source +
        '\n  Installed version : ' + version +
        '\n  Fixed version     : ' + fix +
        '\n';
      security_report_v4(port:port, extra:report, severity:SECURITY_HOLE);
    }
    else audit(AUDIT_LISTEN_NOT_VULN, "PHP", port, version);