RHSA-2014:1826 - Security Advisory

Topic

Updated libvncserver packages that fix multiple security issues are now
available for Red Hat Enterprise Linux 6 and 7.

Red Hat Product Security has rated this update as having Moderate security
impact. Common Vulnerability Scoring System (CVSS) base scores, which give
detailed severity ratings, are available for each vulnerability from the
CVE links in the References section.

Description

LibVNCServer is a library that allows for easy creation of VNC server or
client functionality.

An integer overflow flaw, leading to a heap-based buffer overflow, was
found in the way screen sizes were handled by LibVNCServer. A malicious VNC
server could use this flaw to cause a client to crash or, potentially,
execute arbitrary code in the client. (CVE-2014-6051)

A NULL pointer dereference flaw was found in LibVNCServer's framebuffer
setup. A malicious VNC server could use this flaw to cause a VNC client to
crash. (CVE-2014-6052)

A NULL pointer dereference flaw was found in the way LibVNCServer handled
certain ClientCutText message. A remote attacker could use this flaw to
crash the VNC server by sending a specially crafted ClientCutText message
from a VNC client. (CVE-2014-6053)

A divide-by-zero flaw was found in the way LibVNCServer handled the scaling
factor when it was set to "0". A remote attacker could use this flaw to
crash the VNC server using a malicious VNC client. (CVE-2014-6054)

Two stack-based buffer overflow flaws were found in the way LibVNCServer
handled file transfers. A remote attacker could use this flaw to crash the
VNC server using a malicious VNC client. (CVE-2014-6055)

Red Hat would like to thank oCERT for reporting these issues. oCERT
acknowledges Nicolas Ruff as the original reporter.

All libvncserver users are advised to upgrade to these updated packages,
which contain backported patches to correct these issues. All running
applications linked against libvncserver must be restarted for this update
to take effect.

Solution

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to use the
Red Hat Network to apply this update are available at
https://access.redhat.com/articles/11258

Affected Products

• Red Hat Enterprise Linux Server 7 x86_64
• Red Hat Enterprise Linux Server 6 x86_64
• Red Hat Enterprise Linux Server 6 i386
• 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 for x86_64 - Extended Update Support 7.3 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 6.6 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 6.6 i386
• Red Hat Enterprise Linux Server from RHUI 6 x86_64
• Red Hat Enterprise Linux Server - AUS 7.7 x86_64
• Red Hat Enterprise Linux Server - AUS 7.4 x86_64
• Red Hat Enterprise Linux Server - AUS 7.3 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 i386
• Red Hat Enterprise Linux Workstation 7 x86_64
• Red Hat Enterprise Linux Workstation 6 x86_64
• Red Hat Enterprise Linux Desktop 7 x86_64
• Red Hat Enterprise Linux Desktop 6 x86_64
• Red Hat Enterprise Linux Desktop 6 i386
• Red Hat Enterprise Linux for IBM z Systems 6 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 6.6 s390x
• Red Hat Enterprise Linux for Power, big endian 6 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 6.6 ppc64
• Red Hat Enterprise Linux Server from RHUI 7 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 i386
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 6.6 x86_64
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 6.6 i386
• Red Hat Enterprise Linux Server - AUS 7.6 x86_64
• Red Hat Enterprise Linux Server - AUS 6.6 x86_64
• Red Hat Enterprise Linux Workstation 6 i386
• 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 - TUS 7.3 x86_64
• Red Hat Enterprise Linux Server - TUS 6.6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 6 s390x
• 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
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.3 x86_64

Fixes

• BZ - 1144287 - CVE-2014-6051 libvncserver: integer overflow flaw, leading to a heap-based buffer overflow in screen size handling
• BZ - 1144288 - CVE-2014-6052 libvncserver: NULL pointer dereference flaw in framebuffer setup
• BZ - 1144289 - CVE-2014-6053 libvncserver: server NULL pointer dereference flaw in ClientCutText message handling
• BZ - 1144291 - CVE-2014-6054 libvncserver: server divide-by-zero flaw in scaling factor handling
• BZ - 1144293 - CVE-2014-6055 libvncserver: server stacked-based buffer overflow flaws in file transfer handling

CVEs

• CVE-2014-6053
• CVE-2014-6055
• CVE-2014-6054
• CVE-2014-6051
• CVE-2014-6052

References

• https://access.redhat.com/security/updates/classification/#moderate