Heap-based buffer overflow in ultra.c in LibVNCClient in LibVNCServer before 0.9.11 allows remote servers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted FramebufferUpdate message with the Ultra type tile, such that the LZO payload decompressed length exceeds what is specified by the tile dimensions.

The remote Redhat Enterprise Linux 7 host has one or more packages installed that are affected by multiple vulnerabilities that have been acknowledged by the vendor but will not be patched.

  - libvncserver: Multiple heap out-of-bound writes in VNC client code (Incomplete fix for CVE-2018-20019)     (CVE-2018-20748)

  - Heap-based buffer overflow in rfbproto.c in LibVNCClient in LibVNCServer before 0.9.11 allows remote     servers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted     FramebufferUpdate message containing a subrectangle outside of the client drawing area. (CVE-2016-9941)

  - Heap-based buffer overflow in ultra.c in LibVNCClient in LibVNCServer before 0.9.11 allows remote servers     to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted     FramebufferUpdate message with the Ultra type tile, such that the LZO payload decompressed length exceeds     what is specified by the tile dimensions. (CVE-2016-9942)

Note that Nessus has not tested for these issues but has instead relied on the package manager's report that the package is installed.

The remote Redhat Enterprise Linux 6 host has one or more packages installed that are affected by multiple vulnerabilities that have been acknowledged by the vendor but will not be patched.

  - libvncserver: Improper input sanitization in rfbProcessClientNormalMessage in rfbserver.c (CVE-2018-7225)

  - Heap-based buffer overflow in rfbproto.c in LibVNCClient in LibVNCServer before 0.9.11 allows remote     servers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted     FramebufferUpdate message containing a subrectangle outside of the client drawing area. (CVE-2016-9941)

  - Heap-based buffer overflow in ultra.c in LibVNCClient in LibVNCServer before 0.9.11 allows remote servers     to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted     FramebufferUpdate message with the Ultra type tile, such that the LZO payload decompressed length exceeds     what is specified by the tile dimensions. (CVE-2016-9942)

Note that Nessus has not tested for these issues but has instead relied on the package manager's report that the package is installed.

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

  - Heap-based buffer overflow in ultra.c in LibVNCClient     in LibVNCServer before 0.9.11 allows remote servers to     cause a denial of service (application crash) or     possibly execute arbitrary code via a crafted     FramebufferUpdate message with the Ultra type tile,     such that the LZO payload decompressed length exceeds     what is specified by the tile     dimensions.(CVE-2016-9942)

  - It was discovered that websockets.c in LibVNCServer     prior to 0.9.12 did not properly decode certain     WebSocket frames. A malicious attacker could exploit     this by sending specially crafted WebSocket frames to a     server, causing a heap-based buffer     overflow.(CVE-2017-18922)

  - LibVNC commit before     d01e1bb4246323ba6fcee3b82ef1faa9b1dac82a contains a     memory leak (CWE-655) in VNC server code, which allow     an attacker to read stack memory and can be abused for     information disclosure. Combined with another     vulnerability, it can be used to leak stack memory and     bypass ASLR. This attack appear to be exploitable via     network connectivity. These vulnerabilities have been     fixed in commit     d01e1bb4246323ba6fcee3b82ef1faa9b1dac82a.(CVE-2019-1568     1)

  - A divide by zero issue was found to occur in     libvncserver-0.9.12. A malicious client could use this     flaw to send a specially crafted message that, when     processed by the VNC server, would lead to a floating     point exception, resulting in a denial of     service.(CVE-2020-25708)

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.

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

  - Heap-based buffer overflow in ultra.c in LibVNCClient     in LibVNCServer before 0.9.11 allows remote servers to     cause a denial of service (application crash) or     possibly execute arbitrary code via a crafted     FramebufferUpdate message with the Ultra type tile,     such that the LZO payload decompressed length exceeds     what is specified by the tile     dimensions.(CVE-2016-9942)

  - It was discovered that websockets.c in LibVNCServer     prior to 0.9.12 did not properly decode certain     WebSocket frames. A malicious attacker could exploit     this by sending specially crafted WebSocket frames to a     server, causing a heap-based buffer     overflow.(CVE-2017-18922)

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.

The remote Ubuntu 16.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-4587-1 advisory.

    Nicolas Ruff discovered that iTALC had buffer overflows, divide-by-zero errors and didn't check malloc     return values. A remote attacker could use these issues to cause a denial of service or possibly execute     arbitrary code. (CVE-2014-6051, CVE-2014-6052, CVE-2014-6053, CVE-2014-6054, CVE-2014-6055)

    Josef Gajdusek discovered that iTALC had heap-based buffer overflow vulnerabilities. A remote attacker     could used these issues to cause a denial of service or possibly execute arbitrary code. (CVE-2016-9941,     CVE-2016-9942)

    It was discovered that iTALC had an out-of-bounds write, multiple heap out-of-bounds writes, an infinite     loop, improper initializations, and null pointer vulnerabilities. A remote attacker could used these     issues to cause a denial of service or possibly execute arbitrary code. (CVE-2018-15127, CVE-2018-20019,     CVE-2018-20020, CVE-2018-20021, CVE-2018-20022, CVE-2018-20023, CVE-2018-20024, CVE-2018-20748,     CVE-2018-20749, CVE-2018-20750, CVE-2018-7225, CVE-2019-15681)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

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

Several vulnerabilities have been identified in the VNC code of iTALC, a classroom management software. All vulnerabilities referenced below are issues that have originally been reported against Debian source package libvncserver. The italc source package in Debian ships a custom-patched version of libvncserver, thus libvncserver's security fixes required porting over.

CVE-2014-6051

Integer overflow in the MallocFrameBuffer function in vncviewer.c in LibVNCServer allowed remote VNC servers to cause a denial of service (crash) and possibly executed arbitrary code via an advertisement for a large screen size, which triggered a heap-based buffer overflow.

CVE-2014-6052

The HandleRFBServerMessage function in libvncclient/rfbproto.c in LibVNCServer did not check certain malloc return values, which allowed remote VNC servers to cause a denial of service (application crash) or possibly execute arbitrary code by specifying a large screen size in a (1) FramebufferUpdate, (2) ResizeFrameBuffer, or (3) PalmVNCReSizeFrameBuffer message.

CVE-2014-6053

The rfbProcessClientNormalMessage function in libvncserver/rfbserver.c in LibVNCServer did not properly handle attempts to send a large amount of ClientCutText data, which allowed remote attackers to cause a denial of service (memory consumption or daemon crash) via a crafted message that was processed by using a single unchecked malloc.

CVE-2014-6054

The rfbProcessClientNormalMessage function in libvncserver/rfbserver.c in LibVNCServer allowed remote attackers to cause a denial of service (divide-by-zero error and server crash) via a zero value in the scaling factor in a (1) PalmVNCSetScaleFactor or (2) SetScale message.

CVE-2014-6055

Multiple stack-based buffer overflows in the File Transfer feature in rfbserver.c in LibVNCServer allowed remote authenticated users to cause a denial of service (crash) and possibly execute arbitrary code via a (1) long file or (2) directory name or the (3) FileTime attribute in a rfbFileTransferOffer message.

CVE-2016-9941

Heap-based buffer overflow in rfbproto.c in LibVNCClient in LibVNCServer allowed remote servers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted FramebufferUpdate message containing a subrectangle outside of the client drawing area.

CVE-2016-9942

Heap-based buffer overflow in ultra.c in LibVNCClient in LibVNCServer allowed remote servers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted FramebufferUpdate message with the Ultra type tile, such that the LZO payload decompressed length exceeded what is specified by the tile dimensions.

CVE-2018-6307

LibVNC contained heap use-after-free vulnerability in server code of file transfer extension that can result remote code execution.

CVE-2018-7225

An issue was discovered in LibVNCServer.
rfbProcessClientNormalMessage() in rfbserver.c did not sanitize msg.cct.length, leading to access to uninitialized and potentially sensitive data or possibly unspecified other impact (e.g., an integer overflow) via specially crafted VNC packets.

CVE-2018-15126

LibVNC contained heap use-after-free vulnerability in server code of file transfer extension that can result remote code execution.

CVE-2018-15127

LibVNC contained heap out-of-bound write vulnerability in server code of file transfer extension that can result remote code execution

CVE-2018-20749

LibVNC contained a heap out-of-bounds write vulnerability in libvncserver/rfbserver.c. The fix for CVE-2018-15127 was incomplete.

CVE-2018-20750

LibVNC contained a heap out-of-bounds write vulnerability in libvncserver/rfbserver.c. The fix for CVE-2018-15127 was incomplete.

CVE-2018-20019

LibVNC contained multiple heap out-of-bound write vulnerabilities in VNC client code that can result remote code execution

CVE-2018-20748

LibVNC contained multiple heap out-of-bounds write vulnerabilities in libvncclient/rfbproto.c. The fix for CVE-2018-20019 was incomplete.

CVE-2018-20020

LibVNC contained heap out-of-bound write vulnerability inside structure in VNC client code that can result remote code execution

CVE-2018-20021

LibVNC contained a CWE-835: Infinite loop vulnerability in VNC client code. Vulnerability allows attacker to consume excessive amount of resources like CPU and RAM

CVE-2018-20022

LibVNC contained multiple weaknesses CWE-665: Improper Initialization vulnerability in VNC client code that allowed attackers to read stack memory and could be abused for information disclosure. Combined with another vulnerability, it could be used to leak stack memory layout and in bypassing ASLR.

CVE-2018-20023

LibVNC contained CWE-665: Improper Initialization vulnerability in VNC Repeater client code that allowed attacker to read stack memory and could be abused for information disclosure. Combined with another vulnerability, it could be used to leak stack memory layout and in bypassing ASLR.

CVE-2018-20024

LibVNC contained NULL pointer dereference in VNC client code that could result DoS.

CVE-2019-15681

LibVNC contained a memory leak (CWE-655) in VNC server code, which allowed an attacker to read stack memory and could be abused for information disclosure. Combined with another vulnerability, it could be used to leak stack memory and bypass ASLR. This attack appeared to be exploitable via network connectivity.

For Debian 8 'Jessie', these problems have been fixed in version 1:2.0.2+dfsg1-2+deb8u1.

We recommend that you upgrade your italc packages.

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

LibVNCServer was updated to fix two security issues.

These security issues were fixed :

  - CVE-2018-7225: Missing input sanitization inside     rfbserver.c rfbProcessClientNormalMessage()     (bsc#1081493).

  - CVE-2016-9942: Heap-based buffer overflow in ultra.c     allowed remote servers to cause a denial of service     (application crash) or possibly execute arbitrary code     via a crafted FramebufferUpdate message with the Ultra     type tile, such that the LZO payload decompressed length     exceeds what is specified by the tile dimensions     (bsc#1017712).

  - CVE-2016-9941: Heap-based buffer overflow in rfbproto.c     allowed remote servers to cause a denial of service     (application crash) or possibly execute arbitrary code     via a crafted FramebufferUpdate message containing a     subrectangle outside of the client drawing area     (bsc#1017711). This update was imported from the     SUSE:SLE-12:Update update project.

LibVNCServer was updated to fix two security issues. These security issues were fixed :

  - CVE-2018-7225: Missing input sanitization inside     rfbserver.c rfbProcessClientNormalMessage()     (bsc#1081493).

  - CVE-2016-9942: Heap-based buffer overflow in ultra.c     allowed remote servers to cause a denial of service     (application crash) or possibly execute arbitrary code     via a crafted FramebufferUpdate message with the Ultra     type tile, such that the LZO payload decompressed length     exceeds what is specified by the tile dimensions     (bsc#1017712).

  - CVE-2016-9941: Heap-based buffer overflow in rfbproto.c     allowed remote servers to cause a denial of service     (application crash) or possibly execute arbitrary code     via a crafted FramebufferUpdate message containing a     subrectangle outside of the client drawing area     (bsc#1017711).

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.

Update to latest stable release, include fixes for gnutls and gtk-vnc compatibility.

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.

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

  - Heap-based buffer overflow in ultra.c in LibVNCClient     in LibVNCServer before 0.9.11 allows remote servers to     cause a denial of service (application crash) or     possibly execute arbitrary code via a crafted     FramebufferUpdate message with the Ultra type tile,     such that the LZO payload decompressed length exceeds     what is specified by the tile     dimensions.(CVE-2016-9942,CVE-2016-9941)

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.

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.

The remote host is affected by the vulnerability described in GLSA-201702-24 (LibVNCServer/LibVNCClient: Multiple vulnerabilities)

    Multiple vulnerabilities have been discovered in LibVNCServer and       LibVNCClient. Please review the CVE identifiers referenced below for       details.
  Impact :

    A remote attacker could entice a user to connect to a malicious VNC       server or leverage Man-in-the-Middle attacks to cause the execution of       arbitrary code with the privileges of the user running a VNC client       linked against LibVNCClient.
  Workaround :

    There is no known workaround at this time.

The remote Ubuntu 14.04 LTS / 16.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-3171-1 advisory.

    Josef Gajdusek discovered that the LibVNCServer client library incorrectly handled certain     FrameBufferUpdate messages.

    If a user were tricked into connecting to a malicious server, an attacker could use this issue to cause a     denial of service, or possibly execute arbitrary code. (CVE-2016-9941, CVE-2016-9942)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

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

LibVNCServer was updated to fix two security issues. These security issues were fixed :

  - CVE-2016-9941: Heap-based buffer overflow in rfbproto.c     allowed remote servers to cause a denial of service     (application crash) or possibly execute arbitrary code     via a crafted FramebufferUpdate message containing a     subrectangle outside of the client drawing area     (bsc#1017711)

  - CVE-2016-9942: Heap-based buffer overflow in ultra.c     allowed remote servers to cause a denial of service     (application crash) or possibly execute arbitrary code     via a crafted FramebufferUpdate message with the Ultra     type tile, such that the LZO payload decompressed length     exceeds what is specified by the tile dimensions     (bsc#1017712)

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.

libvnc server reports :

Two unrelated buffer overflows can be used by a malicious server to overwrite parts of the heap and crash the client (or possibly execute arbitrary code).

It was discovered that libvncserver, a collection of libraries used to implement VNC/RFB clients and servers, incorrectly processed incoming network packets. This resulted in several heap-based buffer overflows, allowing a rogue server to either cause a DoS by crashing the client, or potentially execute arbitrary code on the client side.

ID	Name	Product	Family	Severity
199929	RHEL 7 : libvncserver (Unpatched Vulnerability)	Nessus	Red Hat Local Security Checks	critical
199898	RHEL 6 : libvncserver (Unpatched Vulnerability)	Nessus	Red Hat Local Security Checks	critical
146731	EulerOS 2.0 SP2 : libvncserver (EulerOS-SA-2021-1321)	Nessus	Huawei Local Security Checks	critical
146177	EulerOS 2.0 SP5 : libvncserver (EulerOS-SA-2021-1208)	Nessus	Huawei Local Security Checks	critical
145206	EulerOS 2.0 SP3 : libvncserver (EulerOS-SA-2021-1091)	Nessus	Huawei Local Security Checks	critical
141545	Ubuntu 16.04 LTS : iTALC vulnerabilities (USN-4587-1)	Nessus	Ubuntu Local Security Checks	critical
130408	Debian DLA-1979-1 : italc security update	Nessus	Debian Local Security Checks	critical
108743	openSUSE Security Update : LibVNCServer (openSUSE-2018-326)	Nessus	SuSE Local Security Checks	critical
108685	SUSE SLES12 Security Update : LibVNCServer (SUSE-SU-2018:0830-1)	Nessus	SuSE Local Security Checks	critical
101644	Fedora 26 : libvncserver (2017-6125002d79)	Nessus	Fedora Local Security Checks	critical
100440	Fedora 24 : libvncserver (2017-dd5d2381e4)	Nessus	Fedora Local Security Checks	critical
100434	Fedora 25 : libvncserver (2017-0e08170fd3)	Nessus	Fedora Local Security Checks	critical
99891	EulerOS 2.0 SP1 : libvncserver (EulerOS-SA-2017-1046)	Nessus	Huawei 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
97267	GLSA-201702-24 : LibVNCServer/LibVNCClient: Multiple vulnerabilities	Nessus	Gentoo Local Security Checks	critical
96445	Ubuntu 14.04 LTS / 16.04 LTS : LibVNCServer vulnerabilities (USN-3171-1)	Nessus	Ubuntu Local Security Checks	critical
96429	SUSE SLES11 Security Update : LibVNCServer (SUSE-SU-2017:0104-1)	Nessus	SuSE Local Security Checks	critical
96367	FreeBSD : libvncserver -- multiple buffer overflows (64be967a-d379-11e6-a071-001e67f15f5a)	Nessus	FreeBSD Local Security Checks	critical
96318	Debian DSA-3753-1 : libvncserver - security update	Nessus	Debian Local Security Checks	critical

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CVE-2016-9942

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