Vulnerabilities > CVE-2017-6967 - Improper Authentication vulnerability in Neutrinolabs Xrdp 0.9.1

047910
CVSS 7.3 - HIGH
Attack vector
NETWORK
Attack complexity
LOW
Privileges required
NONE
Confidentiality impact
LOW
Integrity impact
LOW
Availability impact
LOW
network
low complexity
neutrinolabs
CWE-287
nessus
NVD
Published: 2017-03-17
Updated: 2020-07-08

Summary

xrdp 0.9.1 calls the PAM function auth_start_session() in an incorrect location, leading to PAM session modules not being properly initialized, with a potential consequence of incorrect configurations or elevation of privileges, aka a pam_limits.so bypass.

Vulnerable Configurations

Part Description Count
Application
Neutrinolabs
1

Common Weakness Enumeration (CWE)

Common Attack Pattern Enumeration and Classification (CAPEC)

  • Authentication Abuse
    An attacker obtains unauthorized access to an application, service or device either through knowledge of the inherent weaknesses of an authentication mechanism, or by exploiting a flaw in the authentication scheme's implementation. In such an attack an authentication mechanism is functioning but a carefully controlled sequence of events causes the mechanism to grant access to the attacker. This attack may exploit assumptions made by the target's authentication procedures, such as assumptions regarding trust relationships or assumptions regarding the generation of secret values. This attack differs from Authentication Bypass attacks in that Authentication Abuse allows the attacker to be certified as a valid user through illegitimate means, while Authentication Bypass allows the user to access protected material without ever being certified as an authenticated user. This attack does not rely on prior sessions established by successfully authenticating users, as relied upon for the "Exploitation of Session Variables, Resource IDs and other Trusted Credentials" attack patterns.
  • Exploiting Trust in Client (aka Make the Client Invisible)
    An attack of this type exploits a programs' vulnerabilities in client/server communication channel authentication and data integrity. It leverages the implicit trust a server places in the client, or more importantly, that which the server believes is the client. An attacker executes this type of attack by placing themselves in the communication channel between client and server such that communication directly to the server is possible where the server believes it is communicating only with a valid client. There are numerous variations of this type of attack.
  • Utilizing REST's Trust in the System Resource to Register Man in the Middle
    This attack utilizes a REST(REpresentational State Transfer)-style applications' trust in the system resources and environment to place man in the middle once SSL is terminated. Rest applications premise is that they leverage existing infrastructure to deliver web services functionality. An example of this is a Rest application that uses HTTP Get methods and receives a HTTP response with an XML document. These Rest style web services are deployed on existing infrastructure such as Apache and IIS web servers with no SOAP stack required. Unfortunately from a security standpoint, there frequently is no interoperable identity security mechanism deployed, so Rest developers often fall back to SSL to deliver security. In large data centers, SSL is typically terminated at the edge of the network - at the firewall, load balancer, or router. Once the SSL is terminated the HTTP request is in the clear (unless developers have hashed or encrypted the values, but this is rare). The attacker can utilize a sniffer such as Wireshark to snapshot the credentials, such as username and password that are passed in the clear once SSL is terminated. Once the attacker gathers these credentials, they can submit requests to the web service provider just as authorized user do. There is not typically an authentication on the client side, beyond what is passed in the request itself so once this is compromised, then this is generally sufficient to compromise the service's authentication scheme.
  • Man in the Middle Attack
    This type of attack targets the communication between two components (typically client and server). The attacker places himself in the communication channel between the two components. Whenever one component attempts to communicate with the other (data flow, authentication challenges, etc.), the data first goes to the attacker, who has the opportunity to observe or alter it, and it is then passed on to the other component as if it was never intercepted. This interposition is transparent leaving the two compromised components unaware of the potential corruption or leakage of their communications. The potential for Man-in-the-Middle attacks yields an implicit lack of trust in communication or identify between two components.

Nessus

  • NASL familyFedora Local Security Checks
    NASL idFEDORA_2017-8EAC23007D.NASL
    descriptionNew upstream version of xorgxrdp and xrdp : New features in xrdp : - RemoteFX codec support is now enabled by default. - Bitmap updates support is now enabled by default. - TLS ciphers suites and version is now logged. - Connected computer name is now logged. - Switched to Xorg (xorgxrdp) as the default backend now. - Miscellaneous RemoteFX codec mode improvements. - Socket directory is configurable at the compile time. Bugfixes in xrdp : - Parallels client for MacOS / iOS can now connect (audio redirection must be disabled on client or xrdp server though). - MS RDP client for iOS can now connect using TLS security layer. - MS RDP client for Android can now connect to xrdp. - Large resolutions (4K) can be used with RemoteFX graphics. - Multiple RemoteApps can be opened throguh NeutrinoRDP proxy. - tls_ciphers in xrdp.ini is not limited to 63 chars anymore, it
    last seen2020-06-05
    modified2017-04-17
    plugin id99413
    published2017-04-17
    reporterThis script is Copyright (C) 2017-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/99413
    titleFedora 24 : 1:xrdp / xorgxrdp (2017-8eac23007d)
    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 FEDORA-2017-8eac23007d.
#

include("compat.inc");

if (description)
{
  script_id(99413);
  script_version("3.4");
  script_set_attribute(attribute:"plugin_modification_date", value:"2020/06/04");

  script_cve_id("CVE-2017-6967");
  script_xref(name:"FEDORA", value:"2017-8eac23007d");

  script_name(english:"Fedora 24 : 1:xrdp / xorgxrdp (2017-8eac23007d)");
  script_summary(english:"Checks rpm output for the updated packages.");

  script_set_attribute(
    attribute:"synopsis", 
    value:"The remote Fedora host is missing one or more security updates."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"New upstream version of xorgxrdp and xrdp :

New features in xrdp :

  - RemoteFX codec support is now enabled by default.

  - Bitmap updates support is now enabled by default.

  - TLS ciphers suites and version is now logged.

  - Connected computer name is now logged.

  - Switched to Xorg (xorgxrdp) as the default backend now.

  - Miscellaneous RemoteFX codec mode improvements.

  - Socket directory is configurable at the compile time.

Bugfixes in xrdp :

  - Parallels client for MacOS / iOS can now connect (audio
    redirection must be disabled on client or xrdp server
    though).

  - MS RDP client for iOS can now connect using TLS security
    layer.

  - MS RDP client for Android can now connect to xrdp.

  - Large resolutions (4K) can be used with RemoteFX
    graphics.

  - Multiple RemoteApps can be opened throguh NeutrinoRDP
    proxy.

  - tls_ciphers in xrdp.ini is not limited to 63 chars
    anymore, it's variable-length.

  - Fixed an issue where tls_ciphers were ignored and rdp
    security layer could be used instead.

  - Kill disconnected sessions feature is working with Xorg
    (xorgxrdp) backend.

  - Miscellaneous code cleanup and memory issues fixes.

Rebuild of xrdp requiring both xorgxrdp and tigervnc-minimal. VNC is
still the default.

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."
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://bodhi.fedoraproject.org/updates/FEDORA-2017-8eac23007d"
  );
  script_set_attribute(
    attribute:"solution", 
    value:"Update the affected 1:xrdp and / or xorgxrdp packages."
  );
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:fedoraproject:fedora:1:xrdp");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:fedoraproject:fedora:xorgxrdp");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:fedoraproject:fedora:24");

  script_set_attribute(attribute:"vuln_publication_date", value:"2017/03/17");
  script_set_attribute(attribute:"patch_publication_date", value:"2017/04/16");
  script_set_attribute(attribute:"plugin_publication_date", value:"2017/04/17");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2017-2020 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 = pregmatch(pattern: "Fedora.*release ([0-9]+)", string:release);
if (isnull(os_ver)) audit(AUDIT_UNKNOWN_APP_VER, "Fedora");
os_ver = os_ver[1];
if (! preg(pattern:"^24([^0-9]|$)", string:os_ver)) audit(AUDIT_OS_NOT, "Fedora 24", "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:"FC24", reference:"xrdp-0.9.2-5.fc24", epoch:"1")) flag++;
if (rpm_check(release:"FC24", reference:"xorgxrdp-0.2.1-1.fc24")) flag++;


if (flag)
{
  security_report_v4(
    port       : 0,
    severity   : SECURITY_HOLE,
    extra      : rpm_report_get()
  );
  exit(0);
}
else
{
  tested = pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, "1:xrdp / xorgxrdp");
}
  • NASL familySuSE Local Security Checks
    NASL idSUSE_SU-2019-1847-1.NASL
    descriptionThis update for xrdp fixes the following issues : These security issues were fixed : CVE-2013-1430: When successfully logging in using RDP into an xrdp session, the file ~/.vnc/sesman_${username}_passwd was created. Its content was the equivalent of the user
    last seen2020-06-01
    modified2020-06-02
    plugin id126738
    published2019-07-16
    reporterThis script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/126738
    titleSUSE SLED12 / SLES12 Security Update : xrdp (SUSE-SU-2019:1847-1)
    code
    #
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from SUSE update advisory SUSE-SU-2019:1847-1.
# The text itself is copyright (C) SUSE.
#

include("compat.inc");

if (description)
{
  script_id(126738);
  script_version("1.3");
  script_cvs_date("Date: 2020/01/08");

  script_cve_id("CVE-2013-1430", "CVE-2017-16927", "CVE-2017-6967");

  script_name(english:"SUSE SLED12 / SLES12 Security Update : xrdp (SUSE-SU-2019:1847-1)");
  script_summary(english:"Checks rpm output for the updated packages.");

  script_set_attribute(
    attribute:"synopsis", 
    value:"The remote SUSE host is missing one or more security updates."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"This update for xrdp fixes the following issues :

These security issues were fixed :

CVE-2013-1430: When successfully logging in using RDP into an xrdp
session, the file ~/.vnc/sesman_${username}_passwd was created. Its
content was the equivalent of the user's cleartext password, DES
encrypted with a known key (bsc#1015567).

CVE-2017-16927: The scp_v0s_accept function in
sesman/libscp/libscp_v0.c in the session manager in xrdp through used
an untrusted integer as a write length, which could lead to a local
denial of service (bsc#1069591).

CVE-2017-6967: Fixed call of the PAM function auth_start_session().
This lead to to PAM session modules not being properly initialized,
with a potential consequence of incorrect configurations or elevation
of privileges, aka a pam_limits.so bypass (bsc#1029912).

The update package also includes non-security fixes. See advisory for
details.

Note that Tenable Network Security has extracted the preceding
description block directly from the SUSE 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.suse.com/show_bug.cgi?id=1014524"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://bugzilla.suse.com/show_bug.cgi?id=1015567"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://bugzilla.suse.com/show_bug.cgi?id=1029912"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://bugzilla.suse.com/show_bug.cgi?id=1060644"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://bugzilla.suse.com/show_bug.cgi?id=1069591"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://bugzilla.suse.com/show_bug.cgi?id=1090174"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://bugzilla.suse.com/show_bug.cgi?id=1100453"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://bugzilla.suse.com/show_bug.cgi?id=1101506"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://www.suse.com/security/cve/CVE-2013-1430/"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://www.suse.com/security/cve/CVE-2017-16927/"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://www.suse.com/security/cve/CVE-2017-6967/"
  );
  # https://www.suse.com/support/update/announcement/2019/suse-su-20191847-1/
  script_set_attribute(
    attribute:"see_also",
    value:"http://www.nessus.org/u?d69cce7d"
  );
  script_set_attribute(
    attribute:"solution", 
    value:
"To install this SUSE Security Update use the SUSE recommended
installation methods like YaST online_update or 'zypper patch'.

Alternatively you can run the command listed for your product :

SUSE Linux Enterprise Server 12-SP4:zypper in -t patch
SUSE-SLE-SERVER-12-SP4-2019-1847=1

SUSE Linux Enterprise Desktop 12-SP4:zypper in -t patch
SUSE-SLE-DESKTOP-12-SP4-2019-1847=1"
  );
  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:L/I:L/A:L");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2017-6967");
  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:novell:suse_linux:xrdp");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:novell:suse_linux:xrdp-debuginfo");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:novell:suse_linux:xrdp-debugsource");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:novell:suse_linux:12");

  script_set_attribute(attribute:"vuln_publication_date", value:"2016/12/16");
  script_set_attribute(attribute:"patch_publication_date", value:"2019/07/15");
  script_set_attribute(attribute:"plugin_publication_date", value:"2019/07/16");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof.");
  script_family(english:"SuSE Local Security Checks");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/cpu", "Host/SuSE/release", "Host/SuSE/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/SuSE/release");
if (isnull(release) || release !~ "^(SLED|SLES)") audit(AUDIT_OS_NOT, "SUSE");
os_ver = pregmatch(pattern: "^(SLE(S|D)\d+)", string:release);
if (isnull(os_ver)) audit(AUDIT_UNKNOWN_APP_VER, "SUSE");
os_ver = os_ver[1];
if (! preg(pattern:"^(SLED12|SLES12)$", string:os_ver)) audit(AUDIT_OS_NOT, "SUSE SLED12 / SLES12", "SUSE " + os_ver);

if (!get_kb_item("Host/SuSE/rpm-list")) audit(AUDIT_PACKAGE_LIST_MISSING);

cpu = get_kb_item("Host/cpu");
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if (cpu !~ "^i[3-6]86$" && "x86_64" >!< cpu && "s390x" >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, "SUSE " + os_ver, cpu);

sp = get_kb_item("Host/SuSE/patchlevel");
if (isnull(sp)) sp = "0";
if (os_ver == "SLES12" && (! preg(pattern:"^(4)$", string:sp))) audit(AUDIT_OS_NOT, "SLES12 SP4", os_ver + " SP" + sp);
if (os_ver == "SLED12" && (! preg(pattern:"^(4)$", string:sp))) audit(AUDIT_OS_NOT, "SLED12 SP4", os_ver + " SP" + sp);


flag = 0;
if (rpm_check(release:"SLES12", sp:"4", reference:"xrdp-0.9.0~git.1456906198.f422461-21.9.1")) flag++;
if (rpm_check(release:"SLES12", sp:"4", reference:"xrdp-debuginfo-0.9.0~git.1456906198.f422461-21.9.1")) flag++;
if (rpm_check(release:"SLES12", sp:"4", reference:"xrdp-debugsource-0.9.0~git.1456906198.f422461-21.9.1")) flag++;
if (rpm_check(release:"SLED12", sp:"4", cpu:"x86_64", reference:"xrdp-0.9.0~git.1456906198.f422461-21.9.1")) flag++;
if (rpm_check(release:"SLED12", sp:"4", cpu:"x86_64", reference:"xrdp-debuginfo-0.9.0~git.1456906198.f422461-21.9.1")) flag++;
if (rpm_check(release:"SLED12", sp:"4", cpu:"x86_64", reference:"xrdp-debugsource-0.9.0~git.1456906198.f422461-21.9.1")) flag++;


if (flag)
{
  if (report_verbosity > 0) security_hole(port:0, extra:rpm_report_get());
  else security_hole(0);
  exit(0);
}
else
{
  tested = pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, "xrdp");
}
  • NASL familyFedora Local Security Checks
    NASL idFEDORA_2017-7BD002B77C.NASL
    descriptionNew upstream version of xorgxrdp and xrdp : New features in xrdp : - RemoteFX codec support is now enabled by default. - Bitmap updates support is now enabled by default. - TLS ciphers suites and version is now logged. - Connected computer name is now logged. - Switched to Xorg (xorgxrdp) as the default backend now. - Miscellaneous RemoteFX codec mode improvements. - Socket directory is configurable at the compile time. Bugfixes in xrdp : - Parallels client for MacOS / iOS can now connect (audio redirection must be disabled on client or xrdp server though). - MS RDP client for iOS can now connect using TLS security layer. - MS RDP client for Android can now connect to xrdp. - Large resolutions (4K) can be used with RemoteFX graphics. - Multiple RemoteApps can be opened throguh NeutrinoRDP proxy. - tls_ciphers in xrdp.ini is not limited to 63 chars anymore, it
    last seen2020-06-05
    modified2017-04-17
    plugin id99411
    published2017-04-17
    reporterThis script is Copyright (C) 2017-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/99411
    titleFedora 25 : 1:xrdp / xorgxrdp (2017-7bd002b77c)
  • NASL familyFedora Local Security Checks
    NASL idFEDORA_2017-FC634E7EE7.NASL
    descriptionNew upstream version of xorgxrdp and xrdp : New features in xrdp : - RemoteFX codec support is now enabled by default. - Bitmap updates support is now enabled by default. - TLS ciphers suites and version is now logged. - Connected computer name is now logged. - Switched to Xorg (xorgxrdp) as the default backend now. - Miscellaneous RemoteFX codec mode improvements. - Socket directory is configurable at the compile time. Bugfixes in xrdp : - Parallels client for MacOS / iOS can now connect (audio redirection must be disabled on client or xrdp server though). - MS RDP client for iOS can now connect using TLS security layer. - MS RDP client for Android can now connect to xrdp. - Large resolutions (4K) can be used with RemoteFX graphics. - Multiple RemoteApps can be opened throguh NeutrinoRDP proxy. - tls_ciphers in xrdp.ini is not limited to 63 chars anymore, it
    last seen2020-06-05
    modified2017-07-17
    plugin id101753
    published2017-07-17
    reporterThis script is Copyright (C) 2017-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/101753
    titleFedora 26 : 1:xrdp / xorgxrdp (2017-fc634e7ee7)
  • NASL familyDebian Local Security Checks
    NASL idDEBIAN_DLA-872.NASL
    descriptionIt was discovered that xrdp, a Remote Desktop Protocol (RDP) server, calls the PAM function auth_start_session() in an incorrect location, leading to PAM session modules not being properly initialized, with a potential consequence of incorrect configurations or elevation of privileges, aka a pam_limits.so bypass. For Debian 7
    last seen2020-03-17
    modified2017-03-28
    plugin id99000
    published2017-03-28
    reporterThis script is Copyright (C) 2017-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/99000
    titleDebian DLA-872-1 : xrdp security update
  • NASL familySuSE Local Security Checks
    NASL idSUSE_SU-2019-1860-1.NASL
    descriptionThis update for xrdp fixes the following issues : Security issues fixed : CVE-2013-1430: When successfully logging in using RDP into an xrdp session, the file ~/.vnc/sesman_${username}_passwd was created. Its content was the equivalent of the user
    last seen2020-06-01
    modified2020-06-02
    plugin id126771
    published2019-07-17
    reporterThis script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/126771
    titleSUSE SLES12 Security Update : xrdp (SUSE-SU-2019:1860-1)

References