# CVE-2026-44988: libvncserver: LibVNCClient is a library for easy implementation of a VNC client

CVE-2026-44988 is fixed in 4 products on 1 platform, first by libvncclient1 0.9.15+dfsg-3ubuntu0.1, released May 27, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-44988
- Priority: High
- CVSS: 8.8 (high)
- EPSS: 0.0024
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 27, 2026

## Description

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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | LibVNCServer opensuse-leap 16.0 | 0.9.14-160000.5.1 | [OPENSUSE-SU-2026:21118-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21118-1.md) | Jun 20, 2026 |
| Linux | LibVNCServer sles 15.7 | 0.9.14-150600.3.9.1 | [SUSE-SU-2026:2427-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-2427-1.md) | Jun 17, 2026 |
| Linux | LibVNCServer sles 16.0 | 0.9.14-160000.5.1 | [SUSE-SU-2026:22190-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-22190-1.md) | Jun 20, 2026 |
| Linux | libvncclient1 Ubuntu 22.04.1 LTS (jammy) | 0.9.13+dfsg-3ubuntu0.1 | [libvncclient1 0.9.13+dfsg-3ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libvncclient1-0.9.13-dfsg-3ubuntu0.1.md) | Jun 24, 2026 |
| Linux | libvncclient1 Ubuntu 24.04.5 LTS (noble) | 0.9.14+dfsg-1ubuntu0.1 | [libvncclient1 0.9.14+dfsg-1ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libvncclient1-0.9.14-dfsg-1ubuntu0.1.md) | Jun 24, 2026 |
| Linux | libvncclient1 Ubuntu 25.10 (questing) | 0.9.15+dfsg-1ubuntu0.1 | [libvncclient1 0.9.15+dfsg-1ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-questing-libvncclient1-0.9.15-dfsg-1ubuntu0.1.md) | Jun 24, 2026 |
| Linux | libvncclient1 Ubuntu 26.04.1 LTS (resolute) | 0.9.15+dfsg-3ubuntu0.1 | [libvncclient1 0.9.15+dfsg-3ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libvncclient1-0.9.15-dfsg-3ubuntu0.1.md) | May 27, 2026 |
| Linux | libvncserver Debian 12.15 (bookworm) | 0.9.14+dfsg-1+deb12u2 | [DEBIAN-CVE-2026-44988](https://patchblox.com/security/data/fix/linux/debian-cve-2026-44988.md) | Jun 24, 2026 |
| Linux | libvncserver Debian 13.5 (trixie) | 0.9.15+dfsg-1+deb13u2 | [DEBIAN-CVE-2026-44988](https://patchblox.com/security/data/fix/linux/debian-cve-2026-44988.md) | Jun 24, 2026 |
| Linux | libvncserver Debian 14 | 0.9.15+dfsg-5 | [DEBIAN-CVE-2026-44988](https://patchblox.com/security/data/fix/linux/debian-cve-2026-44988.md) | Jun 24, 2026 |
| Linux | libvncserver1 Ubuntu 22.04.1 LTS (jammy) | 0.9.13+dfsg-3ubuntu0.1 | [libvncserver1 0.9.13+dfsg-3ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libvncserver1-0.9.13-dfsg-3ubuntu0.1.md) | Jun 24, 2026 |
| Linux | libvncserver1 Ubuntu 24.04.5 LTS (noble) | 0.9.14+dfsg-1ubuntu0.1 | [libvncserver1 0.9.14+dfsg-1ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libvncserver1-0.9.14-dfsg-1ubuntu0.1.md) | Jun 24, 2026 |
| Linux | libvncserver1 Ubuntu 25.10 (questing) | 0.9.15+dfsg-1ubuntu0.1 | [libvncserver1 0.9.15+dfsg-1ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-questing-libvncserver1-0.9.15-dfsg-1ubuntu0.1.md) | Jun 24, 2026 |
| Linux | libvncserver1 Ubuntu 26.04.1 LTS (resolute) | 0.9.15+dfsg-3ubuntu0.1 | [libvncserver1 0.9.15+dfsg-3ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libvncserver1-0.9.15-dfsg-3ubuntu0.1.md) | May 27, 2026 |

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Data as of 2026-11-08T19:12:23Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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