Vulnerabilities > CVE-2016-3116 - Security Bypass vulnerability in Dropbear SSH

047910
CVSS 5.5 - MEDIUM
Attack vector
NETWORK
Attack complexity
LOW
Privileges required
SINGLE
Confidentiality impact
PARTIAL
Integrity impact
PARTIAL
Availability impact
NONE
network
low complexity
dropbear-ssh-project
nessus
exploit available

Summary

CRLF injection vulnerability in Dropbear SSH before 2016.72 allows remote authenticated users to bypass intended shell-command restrictions via crafted X11 forwarding data. <a href="https://cwe.mitre.org/data/definitions/93.html">CWE-93: Improper Neutralization of CRLF Sequences ('CRLF Injection')</a>

Vulnerable Configurations

Part Description Count
Application
Dropbear_Ssh_Project
51

Exploit-Db

descriptionDropBearSSHD <= 2015.71 - Command Injection. CVE-2016-3116. Remote exploit for Linux platform
idEDB-ID:40119
last seen2016-07-18
modified2016-03-03
published2016-03-03
reportertintinweb
sourcehttps://www.exploit-db.com/download/40119/
titleDropBearSSHD <= 2015.71 - Command Injection

Nessus

  • NASL familyFedora Local Security Checks
    NASL idFEDORA_2016-40A657CEE1.NASL
    descriptionCVE-2016-3116 dropbear: X11 forwarding input not validated properly Note that Tenable Network Security has extracted the preceding description block directly from the Fedora security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-06-05
    modified2016-03-24
    plugin id90132
    published2016-03-24
    reporterThis script is Copyright (C) 2016-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/90132
    titleFedora 22 : dropbear-2016.72-1.fc22 (2016-40a657cee1)
    code
    #%NASL_MIN_LEVEL 80502
    #
    # (C) Tenable Network Security, Inc.
    #
    # The descriptive text and package checks in this plugin were  
    # extracted from Fedora Security Advisory 2016-40a657cee1.
    #
    
    include("compat.inc");
    
    if (description)
    {
      script_id(90132);
      script_version("2.4");
      script_set_attribute(attribute:"plugin_modification_date", value:"2020/06/04");
    
      script_cve_id("CVE-2016-3116");
      script_xref(name:"FEDORA", value:"2016-40a657cee1");
    
      script_name(english:"Fedora 22 : dropbear-2016.72-1.fc22 (2016-40a657cee1)");
      script_summary(english:"Checks rpm output for the updated package.");
    
      script_set_attribute(
        attribute:"synopsis", 
        value:"The remote Fedora host is missing a security update."
      );
      script_set_attribute(
        attribute:"description", 
        value:
    "CVE-2016-3116 dropbear: X11 forwarding input not validated properly
    
    Note that Tenable Network Security has extracted the preceding
    description block directly from the Fedora security advisory. Tenable
    has attempted to automatically clean and format it as much as possible
    without introducing additional issues."
      );
      script_set_attribute(
        attribute:"see_also",
        value:"https://bugzilla.redhat.com/show_bug.cgi?id=1316826"
      );
      # https://lists.fedoraproject.org/pipermail/package-announce/2016-March/179269.html
      script_set_attribute(
        attribute:"see_also",
        value:"http://www.nessus.org/u?39f9a2e2"
      );
      script_set_attribute(
        attribute:"solution", 
        value:"Update the affected dropbear package."
      );
      script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:S/C:P/I:P/A:N");
      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:L/UI:N/S:C/C:L/I:L/A:N");
      script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:O/RC:C");
      script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
      script_set_attribute(attribute:"exploit_available", value:"true");
    
      script_set_attribute(attribute:"plugin_type", value:"local");
      script_set_attribute(attribute:"cpe", value:"p-cpe:/a:fedoraproject:fedora:dropbear");
      script_set_attribute(attribute:"cpe", value:"cpe:/o:fedoraproject:fedora:22");
    
      script_set_attribute(attribute:"patch_publication_date", value:"2016/03/23");
      script_set_attribute(attribute:"plugin_publication_date", value:"2016/03/24");
      script_end_attributes();
    
      script_category(ACT_GATHER_INFO);
      script_copyright(english:"This script is Copyright (C) 2016-2020 and is owned by Tenable, Inc. or an Affiliate thereof.");
      script_family(english:"Fedora Local Security Checks");
    
      script_dependencies("ssh_get_info.nasl");
      script_require_keys("Host/local_checks_enabled", "Host/RedHat/release", "Host/RedHat/rpm-list");
    
      exit(0);
    }
    
    
    include("audit.inc");
    include("global_settings.inc");
    include("rpm.inc");
    
    if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
    release = get_kb_item("Host/RedHat/release");
    if (isnull(release) || "Fedora" >!< release) audit(AUDIT_OS_NOT, "Fedora");
    os_ver = eregmatch(pattern: "Fedora.*release ([0-9]+)", string:release);
    if (isnull(os_ver)) audit(AUDIT_UNKNOWN_APP_VER, "Fedora");
    os_ver = os_ver[1];
    if (! ereg(pattern:"^22([^0-9]|$)", string:os_ver)) audit(AUDIT_OS_NOT, "Fedora 22.x", "Fedora " + os_ver);
    
    if (!get_kb_item("Host/RedHat/rpm-list")) audit(AUDIT_PACKAGE_LIST_MISSING);
    
    cpu = get_kb_item("Host/cpu");
    if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
    if ("x86_64" >!< cpu && cpu !~ "^i[3-6]86$") audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, "Fedora", cpu);
    
    flag = 0;
    if (rpm_check(release:"FC22", reference:"dropbear-2016.72-1.fc22")) flag++;
    
    
    if (flag)
    {
      if (report_verbosity > 0) security_warning(port:0, extra:rpm_report_get());
      else security_warning(0);
      exit(0);
    }
    else
    {
      tested = pkg_tests_get();
      if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
      else audit(AUDIT_PACKAGE_NOT_INSTALLED, "dropbear");
    }
    
  • NASL familyMisc.
    NASL idDROPBEAR_SSH_72.NASL
    descriptionAccording to its self-reported version in the banner, the version of Dropbear SSH running on the remote host is prior to 2016.72. It is, therefore, affected by a command injection vulnerability when X11 Forwarding is enabled, due to improper sanitization of X11 authentication credentials. An authenticated, remote attacker can exploit this to execute arbitrary xauth commands on the remote host. Note that X11 Forwarding is not enabled by default.
    last seen2020-06-01
    modified2020-06-02
    plugin id90027
    published2016-03-18
    reporterThis script is Copyright (C) 2016-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/90027
    titleDropbear SSH Server < 2016.72 xauth Command Injection
    code
    #
    # (C) Tenable Network Security, Inc.
    #
    
    include("compat.inc");
    
    if (description)
    {
      script_id(90027);
      script_version("1.7");
      script_cvs_date("Date: 2019/11/20");
    
      script_cve_id("CVE-2016-3116");
    
      script_name(english:"Dropbear SSH Server < 2016.72 xauth Command Injection");
      script_summary(english:"Checks remote SSH server type and version.");
    
      script_set_attribute(attribute:"synopsis", value:
    "The remote SSH service is affected by a command injection
    vulnerability.");
      script_set_attribute(attribute:"description", value:
    "According to its self-reported version in the banner, the version of
    Dropbear SSH running on the remote host is prior to 2016.72. It is,
    therefore, affected by a command injection vulnerability when X11
    Forwarding is enabled, due to improper sanitization of X11
    authentication credentials. An authenticated, remote attacker can
    exploit this to execute arbitrary xauth commands on the remote host.
    
    Note that X11 Forwarding is not enabled by default.");
      script_set_attribute(attribute:"see_also", value:"https://matt.ucc.asn.au/dropbear/CHANGES");
      script_set_attribute(attribute:"see_also", value:"https://seclists.org/fulldisclosure/2016/Mar/47");
      # https://github.com/mkj/dropbear/commit/18681875e30e1ea251914417829fdbb50534c9ba
      script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?c1e20657");
      script_set_attribute(attribute:"solution", value:
    "Upgrade to Dropbear SSH version 2016.72 or later.");
      script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:S/C:P/I:P/A:N");
      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:L/UI:N/S:C/C:L/I:L/A:N");
      script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:O/RC:C");
      script_set_attribute(attribute:"cvss_score_source", value:"CVE-2016-3116");
    
      script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
      script_set_attribute(attribute:"exploit_available", value:"true");
    
      script_set_attribute(attribute:"vuln_publication_date", value:"2016/03/09");
      script_set_attribute(attribute:"patch_publication_date", value:"2016/03/09");
      script_set_attribute(attribute:"plugin_publication_date", value:"2016/03/18");
    
      script_set_attribute(attribute:"potential_vulnerability", value:"true");
      script_set_attribute(attribute:"plugin_type", value:"remote");
      script_set_attribute(attribute:"cpe", value:"cpe:/a:matt_johnston:dropbear_ssh_server");
      script_end_attributes();
    
      script_category(ACT_GATHER_INFO);
      script_family(english:"Misc.");
    
      script_copyright(english:"This script is Copyright (C) 2016-2019 and is owned by Tenable, Inc. or an Affiliate thereof.");
    
      script_dependencies("ssh_detect.nasl");
      script_require_keys("Settings/ParanoidReport");
      script_require_ports("Services/ssh", 22);
    
      exit(0);
    }
    
    include("audit.inc");
    include("backport.inc");
    include("global_settings.inc");
    include("misc_func.inc");
    
    if (report_paranoia < 2) audit(AUDIT_PARANOID);
    
    app = "Dropbear SSH";
    port = get_service(svc:"ssh", exit_on_fail:TRUE);
    
    orig_banner = get_kb_item_or_exit("SSH/banner/" + port);
    banner = get_backport_banner(banner:orig_banner);
    
    # Make sure it's Dropbear.
    if ("dropbear" >!< banner) audit(AUDIT_NOT_DETECT, "Dropbear SSH", port);
    
    if (backported) audit(AUDIT_BACKPORT_SERVICE, port, "Dropbear SSH");
    
    item = eregmatch(pattern:"dropbear_([0-9]+\.[0-9]+(\.[0-9]+)?)($|[^0-9])", string:banner);
    if (isnull(item)) audit(AUDIT_SERVICE_VER_FAIL, "Dropbear SSH", port);
    version = item[1];
    
    #SSH version : SSH-2.0-dropbear_0.53.1
    #SSH version : SSH-2.0-dropbear_2011.54
    if (version =~ "^(0|201[1-5])\.")
    {
      report_items = make_array(
        "Version source", orig_banner,
        "Installed version", version,
        "Fixed version", "2016.72"
      );
      order = make_list("Version source", "Installed version", "Fixed version");
      report = report_items_str(report_items:report_items, ordered_fields:order);
      security_report_v4(severity:SECURITY_WARNING, port:port, extra:report);
    }
    else audit(AUDIT_LISTEN_NOT_VULN, "Dropbear SSH", port, version);
    
  • NASL familySuSE Local Security Checks
    NASL idOPENSUSE-2016-393.NASL
    descriptionThis update for dropbear fixes the following issues : - dropbear was updated to upstream version 2016.72 - Validate X11 forwarding input. Could allow bypass of authorized_keys command= restrictions, found by github.com/tintinweb. Thanks for Damien Miller for a patch. - used as bug fix release for boo#970633 - CVE-2016-3116 - dropbear was updated to upstream version 2015.71 - Fix
    last seen2020-06-05
    modified2016-03-25
    plugin id90168
    published2016-03-25
    reporterThis script is Copyright (C) 2016-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/90168
    titleopenSUSE Security Update : dropbear (openSUSE-2016-393)
  • NASL familyFreeBSD Local Security Checks
    NASL idFREEBSD_PKG_8EB78CDCE9EC11E585BE14DAE9D210B8.NASL
    descriptionMatt Johnson reports : Validate X11 forwarding input. Could allow bypass of authorized_keys command= restrictions
    last seen2020-06-01
    modified2020-06-02
    plugin id89928
    published2016-03-15
    reporterThis script is Copyright (C) 2016-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/89928
    titleFreeBSD : dropbear -- authorized_keys command= bypass (8eb78cdc-e9ec-11e5-85be-14dae9d210b8)
  • NASL familySuSE Local Security Checks
    NASL idOPENSUSE-2016-387.NASL
    descriptiondropbear was updated to 2016.72 to fix the following issues : Changes in dropbear : - updated to upstream version 2016.72 - Validate X11 forwarding input. Could allow bypass of authorized_keys command= restrictions, found by github.com/tintinweb. Thanks for Damien Miller for a patch. - used as bug fix release for boo#970633 - CVE-2016-3116 - updated to upstream version 2015.71 - Fix
    last seen2020-06-05
    modified2016-03-25
    plugin id90165
    published2016-03-25
    reporterThis script is Copyright (C) 2016-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/90165
    titleopenSUSE Security Update : dropbear (openSUSE-2016-387)
  • NASL familyFedora Local Security Checks
    NASL idFEDORA_2016-6DE0B19B3B.NASL
    descriptionnew version Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-06-05
    modified2016-08-02
    plugin id92670
    published2016-08-02
    reporterThis script is Copyright (C) 2016-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/92670
    titleFedora 23 : dropbear (2016-6de0b19b3b)
  • NASL familyFedora Local Security Checks
    NASL idFEDORA_2016-332491DE28.NASL
    descriptionCVE-2016-3116 dropbear: X11 forwarding input not validated properly Note that Tenable Network Security has extracted the preceding description block directly from the Fedora security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-06-05
    modified2016-03-24
    plugin id90129
    published2016-03-24
    reporterThis script is Copyright (C) 2016-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/90129
    titleFedora 23 : dropbear-2016.72-1.fc23 (2016-332491de28)
  • NASL familyGentoo Local Security Checks
    NASL idGENTOO_GLSA-201607-08.NASL
    descriptionThe remote host is affected by the vulnerability described in GLSA-201607-08 (Dropbear: Privilege escalation) A CRLF injection vulnerability in Dropbear SSH allows remote authenticated users to bypass intended shell-command restrictions via crafted X11 forwarding data. Impact : A remote authenticated user could execute arbitrary code with the privileges of the process. Workaround : There is no known workaround at this time.
    last seen2020-06-01
    modified2020-06-02
    plugin id92478
    published2016-07-21
    reporterThis script is Copyright (C) 2016-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/92478
    titleGLSA-201607-08 : Dropbear: Privilege escalation
  • NASL familyFedora Local Security Checks
    NASL idFEDORA_2016-BC45FAA824.NASL
    descriptionCVE-2016-3116 dropbear: X11 forwarding input not validated properly Note that Tenable Network Security has extracted the preceding description block directly from the Fedora security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-06-05
    modified2016-03-28
    plugin id90225
    published2016-03-28
    reporterThis script is Copyright (C) 2016-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/90225
    titleFedora 24 : dropbear-2016.72-1.fc24 (2016-bc45faa824)

Packetstorm

data sourcehttps://packetstormsecurity.com/files/download/136251/dropbearsshd-bypass.txt
idPACKETSTORM:136251
last seen2016-12-05
published2016-03-15
reporterINTREST SEC
sourcehttps://packetstormsecurity.com/files/136251/Dropbear-SSHD-xauth-Command-Injection-Bypass.html
titleDropbear SSHD xauth Command Injection / Bypass