LibVNCClient is a library for easy implementation of a VNC client. In 0.9.15 and earlier, LibVNCClient's Tight encoding decoder uses fixed-size 2048-pixel scratch buffers for the Gradient filter, but it does not reject Tight rectangles whose width is larger than 2048 pixels. A malicious VNC server can send a crafted FramebufferUpdate rectangle using Tight encoding with NoZlib | ExplicitFilter and the Gradient filter. When a LibVNCClient-based client connects, the client processes the server-controlled rectangle width and writes beyond fixed-size Gradient buffers. This vulnerability is fixed with commit 5b270544b85233668b98161323297d418a8f5fd1.

The remote SUSE Linux SLES16 / SLES_SAP16 host has packages installed that are affected by a vulnerability as referenced in the SUSE-SU-2026:22190-1 advisory.

    This update for LibVNCServer fixes the following issue

    - CVE-2026-44988: missing validation of rectangle width in tight gradient decoding can lead to server-     triggered out-of-       bounds write (bsc#1266459).

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

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 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8463-1 advisory.

    It was discovered that LibVNCServer had a memory leak in the client cleanup function. An attacker could     possibly use this issue to cause LibVNCServer to consume memory, leading to a denial of service. This     issue only affected Ubuntu 22.04 LTS. (CVE-2020-29260)

    It was discovered that LibVNCServer did not properly validate bounds when handling UltraZip encoding     subrectangles. A remote attacker could possibly use this issue to obtain sensitive information or cause a     denial of service. This issue only affected Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 25.04.
    (CVE-2026-32853)

    It was discovered that LibVNCServer did not properly validate return values in the HTTP proxy handlers. A     remote attacker could possibly use this issue to cause LibVNCServer to crash, resulting in a denial of     service. This issue only affected Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 25.04. (CVE-2026-32854)

    It was discovered that LibVNCServer did not properly handle Tight encoding gradient filter rectangles. A     remote attacker could use this issue to cause LibVNCServer to crash, resulting in a denial of service, or     possibly execute arbitrary code. (CVE-2026-44988)

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 remote SUSE Linux SLED15 / SLED_SAP15 / SLES15 / SLES_SAP15 host has packages installed that are affected by a vulnerability as referenced in the SUSE-SU-2026:2427-1 advisory.

    - CVE-2026-44988: Fixed missing validation of rectangle width in tight gradient       decoding can lead to server-triggered out-of-bounds write (bsc#1266459).

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

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

The remote SUSE Linux SLES12 host has packages installed that are affected by a vulnerability as referenced in the SUSE- SU-2026:2428-1 advisory.

    - CVE-2026-44988: Fixed missing validation of rectangle width in tight gradient       decoding can lead to server-triggered out-of-bounds write (bsc#1266459).

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

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

The version of libvncserver installed on the remote host is prior to 0.9.9-14. It is, therefore, affected by a vulnerability as referenced in the ALAS2-2026-3331 advisory.

    LibVNCClient is a library for easy implementation of a VNC client. In 0.9.15 and earlier, LibVNCClient's     Tight encoding decoder uses fixed-size 2048-pixel scratch buffers for the Gradient filter, but it does not     reject Tight rectangles whose width is larger than 2048 pixels. A malicious VNC server can send a crafted     FramebufferUpdate rectangle using Tight encoding with NoZlib | ExplicitFilter and the Gradient filter.
    When a LibVNCClient-based client connects, the client processes the server-controlled rectangle width and     writes beyond fixed-size Gradient buffers. This vulnerability is fixed with commit     5b270544b85233668b98161323297d418a8f5fd1. (CVE-2026-44988)

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

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

The version of Tencent Linux installed on the remote TencentOS Server 4 host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the TSSA-2026:0429 advisory.

    Package updates are available for TencentOS Server 4 that fix the following vulnerabilities:

    CVE-2026-44988:
    LibVNCClient is a library for easy implementation of a VNC client. In 0.9.15 and earlier, LibVNCClient's     Tight encoding decoder uses fixed-size 2048-pixel scratch buffers for the Gradient filter, but it does not     reject Tight rectangles whose width is larger than 2048 pixels. A malicious VNC server can send a crafted     FramebufferUpdate rectangle using Tight encoding with NoZlib | ExplicitFilter and the Gradient filter.
    When a LibVNCClient-based client connects, the client processes the server-controlled rectangle width and     writes beyond fixed-size Gradient buffers. This vulnerability is fixed with commit     5b270544b85233668b98161323297d418a8f5fd1.

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

Note that Nessus has not tested for this issue 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.

  - LibVNCClient is a library for easy implementation of a VNC client. In 0.9.15 and earlier, LibVNCClient's     Tight encoding decoder uses fixed-size 2048-pixel scratch buffers for the Gradient filter, but it does not     reject Tight rectangles whose width is larger than 2048 pixels. A malicious VNC server can send a crafted     FramebufferUpdate rectangle using Tight encoding with NoZlib | ExplicitFilter and the Gradient filter.
    When a LibVNCClient-based client connects, the client processes the server-controlled rectangle width and     writes beyond fixed-size Gradient buffers. This vulnerability is fixed with commit     5b270544b85233668b98161323297d418a8f5fd1. (CVE-2026-44988)

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

ID	Name	Product	Family	Severity
322906	SUSE SLES16 Security Update : LibVNCServer (SUSE-SU-2026:22190-1)	Nessus	SuSE Local Security Checks	high
322481	Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS : LibVNCServer vulnerabilities (USN-8463-1)	Nessus	Ubuntu Local Security Checks	medium
321679	SUSE SLED15 / SLES15 Security Update : LibVNCServer (SUSE-SU-2026:2427-1)	Nessus	SuSE Local Security Checks	high
321673	SUSE SLES12 Security Update : LibVNCServer (SUSE-SU-2026:2428-1)	Nessus	SuSE Local Security Checks	high
319854	Amazon Linux 2 : libvncserver, --advisory ALAS2-2026-3331 (ALAS-2026-3331)	Nessus	Amazon Linux Local Security Checks	high
319719	TencentOS Server 4: libvncserver (TSSA-2026:0429)	Nessus	Tencent Local Security Checks	high
317317	Linux Distros Unpatched Vulnerability : CVE-2026-44988	Nessus	Misc.	high

Detections

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CVE-2026-44988

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