Several vulnerabilities have recently been discovered in TightVNC 1.x, an X11 based VNC server/viewer application for Windows and Unix.

CVE-2014-6053

The rfbProcessClientNormalMessage function in rfbserver.c in TightVNC server 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-2018-7225

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-2019-8287

TightVNC code contained global buffer overflow in HandleCoRREBBP macro function, which could potentially have result in code execution. This attack appeared to be exploitable via network connectivity.

(aka CVE-2018-20020/libvncserver)

CVE-2018-20021

TightVNC in vncviewer/rfbproto.c contained a CWE-835: Infinite loop vulnerability. The vulnerability allowed an attacker to consume an excessive amount of resources like CPU and RAM.

CVE-2018-20022

TightVNC's vncviewer 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-2019-15678

TightVNC code version contained heap buffer overflow in rfbServerCutText handler, which could have potentially resulted in code execution. This attack appeared to be exploitable via network connectivity.

(partially aka CVE-2018-20748/libvnvserver)

CVE-2019-15679

TightVNC's vncviewer code contained a heap buffer overflow in InitialiseRFBConnection function, which could have potentially resulted in code execution. This attack appeared to be exploitable via network connectivity.

(partially aka CVE-2018-20748/libvnvserver)

CVE-2019-15680

TightVNC's vncviewer code contained a NULL pointer dereference in HandleZlibBPP function, which could have resulted in Denial of System (DoS). This attack appeared to be exploitable via network connectivity.

CVE-2019-15681

TightVNC contained a memory leak (CWE-655) in VNC server code, which allowed an attacker to read stack memory and could have been abused for information disclosure. Combined with another vulnerability, it could have been 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 1.3.9-6.5+deb8u1.

We recommend that you upgrade your tightvnc 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 Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - TightVNC code version 1.3.10 contains null pointer dereference in HandleZlibBPP function, which results     Denial of System (DoS). This attack appear to be exploitable via network connectivity. (CVE-2019-15680)

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

The version of FreeBSD installed on the remote host is prior to tested version. It is, therefore, affected by multiple vulnerabilities as referenced in the b34c1947-a749-11ed-b24b-1c61b4739ac9 advisory.

  - TightVNC code version 1.3.10 contains heap buffer overflow in rfbServerCutText handler, which can     potentially result code execution.. This attack appear to be exploitable via network connectivity.
    (CVE-2019-15678)

  - TightVNC code version 1.3.10 contains heap buffer overflow in InitialiseRFBConnection function, which can     potentially result code execution. This attack appear to be exploitable via network connectivity.
    (CVE-2019-15679)

  - TightVNC code version 1.3.10 contains null pointer dereference in HandleZlibBPP function, which results     Denial of System (DoS). This attack appear to be exploitable via network connectivity. (CVE-2019-15680)

  - TightVNC code version 1.3.10 contains global buffer overflow in HandleCoRREBBP macro function, which can     potentially result code execution. This attack appear to be exploitable via network connectivity.
    (CVE-2019-8287)

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

The remote SUSE Linux SLES11 host has a package installed that is affected by multiple vulnerabilities as referenced in the SUSE-SU-2019:14235-1 advisory.

  - TightVNC code version 1.3.10 contains heap buffer overflow in rfbServerCutText handler, which can     potentially result code execution.. This attack appear to be exploitable via network connectivity.
    (CVE-2019-15678)

  - TightVNC code version 1.3.10 contains heap buffer overflow in InitialiseRFBConnection function, which can     potentially result code execution. This attack appear to be exploitable via network connectivity.
    (CVE-2019-15679)

  - TightVNC code version 1.3.10 contains null pointer dereference in HandleZlibBPP function, which results     Denial of System (DoS). This attack appear to be exploitable via network connectivity. (CVE-2019-15680)

  - TightVNC code version 1.3.10 contains global buffer overflow in HandleCoRREBBP macro function, which can     potentially result code execution. This attack appear to be exploitable via network connectivity.
    (CVE-2019-8287)

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

The remote Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-4407-1 advisory.

    It was discovered that LibVNCServer incorrectly handled decompressing data. An attacker could possibly use     this issue to cause LibVNCServer to crash, resulting in a denial of service. (CVE-2019-15680)

    It was discovered that an information disclosure vulnerability existed in LibVNCServer when sending a     ServerCutText message. An attacker could possibly use this issue to expose sensitive information. This     issue only affected Ubuntu 19.10, Ubuntu 18.04 LTS, and Ubuntu 16.04 LTS. (CVE-2019-15681)

    It was discovered that LibVNCServer incorrectly handled cursor shape updates. If a user were tricked in to     connecting to a malicious server, an attacker could possibly use this issue to cause LibVNCServer to     crash, resulting in a denial of service, or possibly execute arbitrary code. This issue only affected     Ubuntu 19.10, Ubuntu 18.04 LTS, and Ubuntu 16.04 LTS. (CVE-2019-15690, CVE-2019-20788)

    It was discovered that LibVNCServer incorrectly handled decoding WebSocket frames. An attacker could     possibly use this issue to cause LibVNCServer to crash, resulting in a denial of service, or possibly     execute arbitrary code. This issue only affected Ubuntu 19.10, Ubuntu 18.04 LTS, and Ubuntu 16.04 LTS.
    (CVE-2017-18922)

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
132345	Debian DLA-2045-1 : tightvnc security update	Nessus	Debian Local Security Checks	12/23/2019	4/2/2024	critical
258905	Linux Distros Unpatched Vulnerability : CVE-2019-15680	Nessus	Misc.	8/30/2025	10/14/2025	high
171121	FreeBSD : TightVNC -- Muliple Vulnerabilities (b34c1947-a749-11ed-b24b-1c61b4739ac9)	Nessus	FreeBSD Local Security Checks	2/8/2023	2/8/2023	critical
150552	SUSE SLES11 Security Update : tightvnc (SUSE-SU-2019:14235-1)	Nessus	SuSE Local Security Checks	6/10/2021	6/10/2021	critical
138132	Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS : LibVNCServer vulnerabilities (USN-4407-1)	Nessus	Ubuntu Local Security Checks	7/6/2020	9/3/2025	critical

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