The remote Ubuntu 16.04 LTS host has a package installed that is affected by multiple vulnerabilities as referenced in the USN-4547-2 advisory.

    It was discovered that the LibVNCClient vendored in SSVNC incorrectly handled certain packet lengths. A     remote attacker could possibly use this issue to obtain sensitive information, cause a denial of service,     or execute arbitrary code. (CVE-2018-20020, CVE-2018-20021, CVE-2018-20022, CVE-2018-2024)

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.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - LibVNC before 2f5b2ad1c6c99b1ac6482c95844a84d66bb52838 contains multiple weaknesses CWE-665: Improper     Initialization vulnerability in VNC client code that allows attacker to read stack memory and can be abuse     for information disclosure. Combined with another vulnerability, it can be used to leak stack memory     layout and in bypassing ASLR (CVE-2018-20022)

Note that Nessus relies on the presence of the package as reported by the vendor.

This update for LibVNCServer fixes the following issues :

Security issues fixed :

CVE-2018-15126: Fixed use-after-free in file transfer extension (bsc#1120114)

CVE-2018-6307: Fixed use-after-free in file transfer extension server code (bsc#1120115)

CVE-2018-20020: Fixed heap out-of-bound write inside structure in VNC client code (bsc#1120116)

CVE-2018-15127: Fixed heap out-of-bounds write in rfbserver.c (bsc#1120117)

CVE-2018-20019: Fixed multiple heap out-of-bound writes in VNC client code (bsc#1120118)

CVE-2018-20023: Fixed information disclosure through improper initialization in VNC Repeater client code (bsc#1120119)

CVE-2018-20022: Fixed information disclosure through improper initialization in VNC client code (bsc#1120120)

CVE-2018-20024: Fixed NULL pointer dereference in VNC client code (bsc#1120121)

CVE-2018-20021: Fixed infinite loop in VNC client code (bsc#1120122)

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 LibVNCServer fixes the following issues :

Security issues fixed :

CVE-2018-15126: Fixed use-after-free in file transfer extension (bsc#1120114)

CVE-2018-6307: Fixed use-after-free in file transfer extension server code (bsc#1120115)

CVE-2018-20020: Fixed heap out-of-bound write inside structure in VNC client code (bsc#1120116)

CVE-2018-15127: Fixed heap out-of-bounds write in rfbserver.c (bsc#1120117)

CVE-2018-20019: Fixed multiple heap out-of-bound writes in VNC client code (bsc#1120118)

CVE-2018-20022: Fixed information disclosure through improper initialization in VNC client code (bsc#1120120)

CVE-2018-20024: Fixed NULL pointer dereference in VNC client code (bsc#1120121)

CVE-2018-20021: Fixed infinite loop in VNC client code (bsc#1120122)

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 LibVNCServer fixes the following issues :

Security issues fixed :

  - CVE-2018-15126: Fixed use-after-free in file transfer     extension (bsc#1120114)

  - CVE-2018-6307: Fixed use-after-free in file transfer     extension server code (bsc#1120115)

  - CVE-2018-20020: Fixed heap out-of-bound write inside     structure in VNC client code (bsc#1120116)

  - CVE-2018-15127: Fixed heap out-of-bounds write in     rfbserver.c (bsc#1120117)

  - CVE-2018-20019: Fixed multiple heap out-of-bound writes     in VNC client code (bsc#1120118)

  - CVE-2018-20023: Fixed information disclosure through     improper initialization in VNC Repeater client code     (bsc#1120119)

  - CVE-2018-20022: Fixed information disclosure through     improper initialization in VNC client code (bsc#1120120)

  - CVE-2018-20024: Fixed NULL pointer dereference in VNC     client code (bsc#1120121)

  - CVE-2018-20021: Fixed infinite loop in VNC client code     (bsc#1120122)

This update was imported from the SUSE:SLE-15:Update update project.

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.

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.

ID	Name	Product	Family	Published	Updated	Severity
140929	Ubuntu 16.04 LTS : SSVNC vulnerabilities (USN-4547-2)	Nessus	Ubuntu Local Security Checks	9/29/2020	8/27/2024	critical
222323	Linux Distros Unpatched Vulnerability : CVE-2018-20022	Nessus	Misc.	3/4/2025	10/27/2025	high
121094	SUSE SLES12 Security Update : LibVNCServer (SUSE-SU-2019:0060-1)	Nessus	SuSE Local Security Checks	1/11/2019	1/13/2021	critical
121160	SUSE SLES11 Security Update : LibVNCServer (SUSE-SU-2019:13927-1)	Nessus	SuSE Local Security Checks	1/14/2019	1/19/2021	critical
121158	SUSE SLED15 / SLES15 Security Update : LibVNCServer (SUSE-SU-2019:0080-1)	Nessus	SuSE Local Security Checks	1/14/2019	1/13/2021	critical
121282	openSUSE Security Update : LibVNCServer (openSUSE-2019-53)	Nessus	SuSE Local Security Checks	1/22/2019	1/19/2021	critical
130408	Debian DLA-1979-1 : italc security update	Nessus	Debian Local Security Checks	10/31/2019	4/16/2024	critical
141545	Ubuntu 16.04 LTS : iTALC vulnerabilities (USN-4587-1)	Nessus	Ubuntu Local Security Checks	10/20/2020	8/27/2024	critical

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