RHSA-2017:2000 - Security Advisory

Topic

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.

Description

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.

Solution

For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

Affected Products

• Red Hat Enterprise Linux Server 7 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.7 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.6 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.5 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.4 x86_64
• Red Hat Enterprise Linux Server - AUS 7.4 x86_64
• Red Hat Enterprise Linux Workstation 7 x86_64
• Red Hat Enterprise Linux Desktop 7 x86_64
• Red Hat Enterprise Linux for IBM z Systems 7 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.7 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.6 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.5 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.4 s390x
• Red Hat Enterprise Linux for Power, big endian 7 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.7 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.6 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.5 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.4 ppc64
• Red Hat Enterprise Linux for Scientific Computing 7 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.7 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.6 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.5 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.4 x86_64
• Red Hat Enterprise Linux Server - AUS 7.7 x86_64
• Red Hat Enterprise Linux Server - AUS 7.6 x86_64
• Red Hat Enterprise Linux for Power, little endian 7 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.7 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.6 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.5 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.4 ppc64le
• Red Hat Enterprise Linux Server - TUS 7.7 x86_64
• Red Hat Enterprise Linux Server - TUS 7.6 x86_64
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 7.7 ppc64le
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 7.6 ppc64le
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 7.4 ppc64le
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.7 x86_64
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.6 x86_64
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.4 x86_64

Fixes

• BZ - 1343899 - Disabling vncconfig window
• BZ - 1358090 - shared memory leakage in vncviewer
• BZ - 1388620 - [REBASE] Tigervnc from 1.3 to 1.8
• BZ - 1393971 - [RFE] systemd unit for Xvnc (not vncserver)
• BZ - 1410164 - tigervnc-server fails to remove /tmp files if not gracefully shut down
• BZ - 1413598 - [REBASE] Update fltk to 1.3.4 for tigervnc
• BZ - 1415547 - Rebuilding tigervnc SRPM stops at applying Patch101
• BZ - 1415712 - CVE-2017-5581 tigervnc: Buffer overflow in ModifiablePixelBuffer::fillRect
• BZ - 1418761 - CVE-2016-10207 tigervnc: VNC server can crash when TLS handshake terminates early
• BZ - 1438694 - CVE-2017-7392 tigervnc: SSecurityVeNCrypt memory leak
• BZ - 1438697 - CVE-2017-7393 tigervnc: Double free via crafted fences
• BZ - 1438700 - CVE-2017-7394 tigervnc: Server crash via long usernames
• BZ - 1438701 - CVE-2017-7395 tigervnc: Integer overflow in SMsgReader::readClientCutText
• BZ - 1438703 - CVE-2017-7396 tigervnc: SecurityServer and ClientServer memory leaks

CVEs

• CVE-2016-10207
• CVE-2017-5581
• CVE-2017-7392
• CVE-2017-7393
• CVE-2017-7394
• CVE-2017-7395
• CVE-2017-7396

References

• https://access.redhat.com/security/updates/classification/#moderate
• https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/7.4_Release_Notes/index.html