The Xvnc server in TigerVNC allows remote attackers to cause a denial of service (invalid memory access and crash) by terminating a TLS handshake early.

The remote NewStart CGSL host, running version MAIN 4.05, has tigervnc packages installed that are affected by multiple vulnerabilities:

  - A buffer overflow flaw, leading to memory corruption,     was found in TigerVNC viewer. A remote malicious VNC     server could use this flaw to crash the client vncviewer     process resulting in denial of service. (CVE-2017-5581)

  - A denial of service flaw was found in the TigerVNC's     Xvnc server. A remote unauthenticated attacker could use     this flaw to make Xvnc crash by terminating the TLS     handshake process early. (CVE-2016-10207)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote host is affected by the vulnerability described in GLSA-201801-13 (TigerVNC: Multiple vulnerabilities)

    Multiple vulnerabilities have been discovered in TigerVNC. Please review       the referenced CVE Identifiers for details.
  Impact :

    An attacker could execute arbitrary code or cause a Denial of Service       condition.
  Workaround :

    There is no known workaround at this time.

According to the versions of the tigervnc packages installed, the EulerOS installation on the remote host is affected by the following vulnerabilities :

  - A denial of service flaw was found in the TigerVNC's     Xvnc server. A remote unauthenticated attacker could     use this flaw to make Xvnc crash by terminating the TLS     handshake process early. (CVE-2016-10207)

  - A double free flaw was found in the way TigerVNC     handled ClientFence messages. A remote, authenticated     attacker could use this flaw to make Xvnc crash by     sending specially crafted ClientFence messages,     resulting in denial of service. (CVE-2017-7393)

  - A missing input sanitization flaw was found in the way     TigerVNC handled credentials. A remote unauthenticated     attacker could use this flaw to make Xvnc crash by     sending specially crafted usernames, resulting in     denial of service. (CVE-2017-7394)

  - An integer overflow flaw was found in the way TigerVNC     handled ClientCutText messages. A remote, authenticated     attacker could use this flaw to make Xvnc crash by     sending specially crafted ClientCutText messages,     resulting in denial of service. (CVE-2017-7395)

  - A buffer overflow flaw, leading to memory corruption,     was found in TigerVNC viewer. A remote malicious VNC     server could use this flaw to crash the client     vncviewer process resulting in denial of service.
    (CVE-2017-5581)

  - A memory leak flaw was found in the way TigerVNC     handled termination of VeNCrypt connections. A remote     unauthenticated attacker could repeatedly send     connection requests to the Xvnc server, causing it to     consume large amounts of memory resources over time,     and ultimately leading to a denial of service due to     memory exhaustion. (CVE-2017-7392)

  - A memory leak flaw was found in the way TigerVNC     handled client connections. A remote unauthenticated     attacker could repeatedly send connection requests to     the Xvnc server, causing it to consume large amounts of     memory resources over time, and ultimately leading to a     denial of service due to memory exhaustion.
    (CVE-2017-7396)

Note that Tenable Network Security has extracted the preceding description block directly from the EulerOS security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

Buffer overflow in ModifiablePixelBuffer::fillRect

A buffer overflow flaw, leading to memory corruption, was found in TigerVNC viewer. A remote malicious VNC server could use this flaw to crash the client vncviewer process resulting in denial of service.
(CVE-2017-5581)

VNC server can crash when TLS handshake terminates early :

A denial of service flaw was found in the TigerVNC's Xvnc server. A remote unauthenticated attacker could use this flaw to make Xvnc crash by terminating the TLS handshake process early. (CVE-2016-10207)

SSecurityVeNCrypt memory leak :

A memory leak flaw was found in the way TigerVNC handled termination of VeNCrypt connections. A remote unauthenticated attacker could repeatedly send connection requests to the Xvnc server, causing it to consume large amounts of memory resources over time, and ultimately leading to a denial of service due to memory exhaustion.
(CVE-2017-7392)

Double free via crafted fences :

A double free flaw was found in the way TigerVNC handled ClientFence messages. A remote, authenticated attacker could use this flaw to make Xvnc crash by sending specially crafted ClientFence messages, resulting in denial of service. (CVE-2017-7393)

Server crash via long usernames :

A missing input sanitization flaw was found in the way TigerVNC handled credentials. A remote unauthenticated attacker could use this flaw to make Xvnc crash by sending specially crafted usernames, resulting in denial of service. (CVE-2017-7394)

Integer overflow in SMsgReader::readClientCutText :

An integer overflow flaw was found in the way TigerVNC handled ClientCutText messages. A remote, authenticated attacker could use this flaw to make Xvnc crash by sending specially crafted ClientCutText messages, resulting in denial of service.
(CVE-2017-7395)

SecurityServer and ClientServer memory leaks :

A memory leak flaw was found in the way TigerVNC handled client connections. A remote unauthenticated attacker could repeatedly send connection requests to the Xvnc server, causing it to consume large amounts of memory resources over time, and ultimately leading to a denial of service due to memory exhaustion. (CVE-2017-7396)

An update for tigervnc and fltk is now available for Red Hat Enterprise Linux 7.

Red Hat Product Security has rated this update as having a security impact of Moderate. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Virtual Network Computing (VNC) is a remote display system which allows users to view a computing desktop environment not only on the machine where it is running, but from anywhere on the Internet and from a wide variety of machine architectures. TigerVNC is a suite of VNC servers and clients which allows users to connect to other desktops running a VNC server.

FLTK (pronounced 'fulltick') is a cross-platform C++ GUI toolkit. It provides modern GUI functionality without the bloat, and supports 3D graphics via OpenGL and its built-in GLUT emulation.

The following packages have been upgraded to a later upstream version:
tigervnc (1.8.0), fltk (1.3.4). (BZ#1388620, BZ#1413598)

Security Fix(es) :

* A denial of service flaw was found in the TigerVNC's Xvnc server. A remote unauthenticated attacker could use this flaw to make Xvnc crash by terminating the TLS handshake process early. (CVE-2016-10207)

* A double free flaw was found in the way TigerVNC handled ClientFence messages. A remote, authenticated attacker could use this flaw to make Xvnc crash by sending specially crafted ClientFence messages, resulting in denial of service. (CVE-2017-7393)

* A missing input sanitization flaw was found in the way TigerVNC handled credentials. A remote unauthenticated attacker could use this flaw to make Xvnc crash by sending specially crafted usernames, resulting in denial of service. (CVE-2017-7394)

* An integer overflow flaw was found in the way TigerVNC handled ClientCutText messages. A remote, authenticated attacker could use this flaw to make Xvnc crash by sending specially crafted ClientCutText messages, resulting in denial of service.
(CVE-2017-7395)

* A buffer overflow flaw, leading to memory corruption, was found in TigerVNC viewer. A remote malicious VNC server could use this flaw to crash the client vncviewer process resulting in denial of service.
(CVE-2017-5581)

* A memory leak flaw was found in the way TigerVNC handled termination of VeNCrypt connections. A remote unauthenticated attacker could repeatedly send connection requests to the Xvnc server, causing it to consume large amounts of memory resources over time, and ultimately leading to a denial of service due to memory exhaustion.
(CVE-2017-7392)

* A memory leak flaw was found in the way TigerVNC handled client connections. A remote unauthenticated attacker could repeatedly send connection requests to the Xvnc server, causing it to consume large amounts of memory resources over time, and ultimately leading to a denial of service due to memory exhaustion. (CVE-2017-7396)

Additional Changes :

For detailed information on changes in this release, see the Red Hat Enterprise Linux 7.4 Release Notes linked from the References section.

FLTK (pronounced 'fulltick') is a cross-platform C++ GUI toolkit. It provides modern GUI functionality without the bloat, and supports 3D graphics via OpenGL and its built-in GLUT emulation.

The following packages have been upgraded to a later upstream version:
tigervnc (1.8.0), fltk (1.3.4).

Security Fix(es) :

  - A denial of service flaw was found in the TigerVNC's     Xvnc server. A remote unauthenticated attacker could use     this flaw to make Xvnc crash by terminating the TLS     handshake process early. (CVE-2016-10207)

  - A double free flaw was found in the way TigerVNC handled     ClientFence messages. A remote, authenticated attacker     could use this flaw to make Xvnc crash by sending     specially crafted ClientFence messages, resulting in     denial of service. (CVE-2017-7393)

  - A missing input sanitization flaw was found in the way     TigerVNC handled credentials. A remote unauthenticated     attacker could use this flaw to make Xvnc crash by     sending specially crafted usernames, resulting in denial     of service. (CVE-2017-7394)

  - An integer overflow flaw was found in the way TigerVNC     handled ClientCutText messages. A remote, authenticated     attacker could use this flaw to make Xvnc crash by     sending specially crafted ClientCutText messages,     resulting in denial of service. (CVE-2017-7395)

  - A buffer overflow flaw, leading to memory corruption,     was found in TigerVNC viewer. A remote malicious VNC     server could use this flaw to crash the client vncviewer     process resulting in denial of service. (CVE-2017-5581)

  - A memory leak flaw was found in the way TigerVNC handled     termination of VeNCrypt connections. A remote     unauthenticated attacker could repeatedly send     connection requests to the Xvnc server, causing it to     consume large amounts of memory resources over time, and     ultimately leading to a denial of service due to memory     exhaustion. (CVE-2017-7392)

  - A memory leak flaw was found in the way TigerVNC handled     client connections. A remote unauthenticated attacker     could repeatedly send connection requests to the Xvnc     server, causing it to consume large amounts of memory     resources over time, and ultimately leading to a denial     of service due to memory exhaustion. (CVE-2017-7396)

From Red Hat Security Advisory 2017:2000 :

An update for tigervnc and fltk is now available for Red Hat Enterprise Linux 7.

Red Hat Product Security has rated this update as having a security impact of Moderate. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Virtual Network Computing (VNC) is a remote display system which allows users to view a computing desktop environment not only on the machine where it is running, but from anywhere on the Internet and from a wide variety of machine architectures. TigerVNC is a suite of VNC servers and clients which allows users to connect to other desktops running a VNC server.

FLTK (pronounced 'fulltick') is a cross-platform C++ GUI toolkit. It provides modern GUI functionality without the bloat, and supports 3D graphics via OpenGL and its built-in GLUT emulation.

The following packages have been upgraded to a later upstream version:
tigervnc (1.8.0), fltk (1.3.4). (BZ#1388620, BZ#1413598)

Security Fix(es) :

* A denial of service flaw was found in the TigerVNC's Xvnc server. A remote unauthenticated attacker could use this flaw to make Xvnc crash by terminating the TLS handshake process early. (CVE-2016-10207)

* A double free flaw was found in the way TigerVNC handled ClientFence messages. A remote, authenticated attacker could use this flaw to make Xvnc crash by sending specially crafted ClientFence messages, resulting in denial of service. (CVE-2017-7393)

* A missing input sanitization flaw was found in the way TigerVNC handled credentials. A remote unauthenticated attacker could use this flaw to make Xvnc crash by sending specially crafted usernames, resulting in denial of service. (CVE-2017-7394)

* An integer overflow flaw was found in the way TigerVNC handled ClientCutText messages. A remote, authenticated attacker could use this flaw to make Xvnc crash by sending specially crafted ClientCutText messages, resulting in denial of service.
(CVE-2017-7395)

* A buffer overflow flaw, leading to memory corruption, was found in TigerVNC viewer. A remote malicious VNC server could use this flaw to crash the client vncviewer process resulting in denial of service.
(CVE-2017-5581)

* A memory leak flaw was found in the way TigerVNC handled termination of VeNCrypt connections. A remote unauthenticated attacker could repeatedly send connection requests to the Xvnc server, causing it to consume large amounts of memory resources over time, and ultimately leading to a denial of service due to memory exhaustion.
(CVE-2017-7392)

* A memory leak flaw was found in the way TigerVNC handled client connections. A remote unauthenticated attacker could repeatedly send connection requests to the Xvnc server, causing it to consume large amounts of memory resources over time, and ultimately leading to a denial of service due to memory exhaustion. (CVE-2017-7396)

Additional Changes :

For detailed information on changes in this release, see the Red Hat Enterprise Linux 7.4 Release Notes linked from the References section.

Security Fix(es) :

  - A denial of service flaw was found in the TigerVNC's     Xvnc server. A remote unauthenticated attacker could use     this flaw to make Xvnc crash by terminating the TLS     handshake process early. (CVE-2016-10207)

  - A buffer overflow flaw, leading to memory corruption,     was found in TigerVNC viewer. A remote malicious VNC     server could use this flaw to crash the client vncviewer     process resulting in denial of service. (CVE-2017-5581)

From Red Hat Security Advisory 2017:0630 :

An update for tigervnc is now available for Red Hat Enterprise Linux 6.

Red Hat Product Security has rated this update as having a security impact of Moderate. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Virtual Network Computing (VNC) is a remote display system which allows users to view a computing desktop environment not only on the machine where it is running, but from anywhere on the Internet and from a wide variety of machine architectures. TigerVNC is a suite of VNC servers and clients. The tigervnc packages contain a client which allows users to connect to other desktops running a VNC server.

Security Fix(es) :

* A denial of service flaw was found in the TigerVNC's Xvnc server. A remote unauthenticated attacker could use this flaw to make Xvnc crash by terminating the TLS handshake process early. (CVE-2016-10207)

* A buffer overflow flaw, leading to memory corruption, was found in TigerVNC viewer. A remote malicious VNC server could use this flaw to crash the client vncviewer process resulting in denial of service.
(CVE-2017-5581)

Additional Changes :

For detailed information on changes in this release, see the Red Hat Enterprise Linux 6.9 Release Notes and Red Hat Enterprise Linux 6.9 Technical Notes linked from the References section.

An update for tigervnc is now available for Red Hat Enterprise Linux 6.

Red Hat Product Security has rated this update as having a security impact of Moderate. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Virtual Network Computing (VNC) is a remote display system which allows users to view a computing desktop environment not only on the machine where it is running, but from anywhere on the Internet and from a wide variety of machine architectures. TigerVNC is a suite of VNC servers and clients. The tigervnc packages contain a client which allows users to connect to other desktops running a VNC server.

Security Fix(es) :

* A denial of service flaw was found in the TigerVNC's Xvnc server. A remote unauthenticated attacker could use this flaw to make Xvnc crash by terminating the TLS handshake process early. (CVE-2016-10207)

* A buffer overflow flaw, leading to memory corruption, was found in TigerVNC viewer. A remote malicious VNC server could use this flaw to crash the client vncviewer process resulting in denial of service.
(CVE-2017-5581)

Additional Changes :

For detailed information on changes in this release, see the Red Hat Enterprise Linux 6.9 Release Notes and Red Hat Enterprise Linux 6.9 Technical Notes linked from the References section.

This update for tigervnc provides the following fixes :

  - Prevent malicious server from crashing a server via a     buffer overflow, a similar flaw as the LibVNCServer     issues CVE-2016-9941 and CVE-2016-9942. (bsc#1019274)

  - CVE-2016-10207: Prevent potential crash due to     insufficient clean-up after failure to establish TLS     connection. (bsc#1023012)

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.

This update for tigervnc provides the following fixes :

  - Prevent malicious server from crashing a server via a     buffer overflow, a similar flaw as the LibVNCServer     issues CVE-2016-9941 and CVE-2016-9942.. (bsc#1019274)

  - CVE-2016-10207: Prevent potential crash due to     insufficient clean-up after failure to establish TLS     connection. (bsc#1023012)

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.

This update for tigervnc fixes the following issues :

This security issue was fixed :

  - CVE-2016-10207: Prevent crash caused by failed TLS     connection (bnc#1023012)

This non-security issue was fixed :

  - Fix random client disconnections (boo#1022432)

ID	Name	Product	Family	Severity
127339	NewStart CGSL MAIN 4.05 : tigervnc Multiple Vulnerabilities (NS-SA-2019-0106)	Nessus	NewStart CGSL Local Security Checks	critical
105757	GLSA-201801-13 : TigerVNC: Multiple vulnerabilities	Nessus	Gentoo Local Security Checks	high
103086	EulerOS 2.0 SP2 : tigervnc (EulerOS-SA-2017-1228)	Nessus	Huawei Local Security Checks	critical
103085	EulerOS 2.0 SP1 : tigervnc (EulerOS-SA-2017-1227)	Nessus	Huawei Local Security Checks	critical
102867	Amazon Linux AMI : tigervnc (ALAS-2017-879)	Nessus	Amazon Linux Local Security Checks	critical
102748	CentOS 7 : fltk / tigervnc (CESA-2017:2000)	Nessus	CentOS Local Security Checks	critical
102658	Scientific Linux Security Update : tigervnc and fltk on SL7.x x86_64 (20170801)	Nessus	Scientific Linux Local Security Checks	critical
102293	Oracle Linux 7 : fltk / tigervnc (ELSA-2017-2000)	Nessus	Oracle Linux Local Security Checks	critical
102109	RHEL 7 : tigervnc and fltk (RHSA-2017:2000)	Nessus	Red Hat Local Security Checks	critical
99227	Scientific Linux Security Update : tigervnc on SL6.x i386/x86_64 (20170321)	Nessus	Scientific Linux Local Security Checks	critical
99065	Oracle Linux 6 : tigervnc (ELSA-2017-0630)	Nessus	Oracle Linux Local Security Checks	critical
97953	CentOS 6 : tigervnc (CESA-2017:0630)	Nessus	CentOS Local Security Checks	critical
97876	RHEL 6 : tigervnc (RHSA-2017:0630)	Nessus	Red Hat Local Security Checks	critical
97598	SUSE SLED12 / SLES12 Security Update : tigervnc (SUSE-SU-2017:0622-1)	Nessus	SuSE Local Security Checks	critical
97299	SUSE SLED12 / SLES12 Security Update : tigervnc (SUSE-SU-2017:0519-1)	Nessus	SuSE Local Security Checks	critical
97115	openSUSE Security Update : tigervnc (openSUSE-2017-243)	Nessus	SuSE Local Security Checks	high

Detections

Analytics

CVE-2016-10207

high

Tenable Plugins

critical

high

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high