CVE-2026-44988 Details
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.
A vulnerability in LibVNCClient versions through 0.9.15 allows for out-of-bounds writes due to improper handling of Tight encoding rectangles in the Gradient filter. The decoder uses fixed-size buffers for the Gradient filter but fails to reject rectangles wider than 2048 pixels. This oversight enables a malicious VNC server to send crafted FramebufferUpdate rectangles that exploit the buffer size limitation, leading to memory corruption.
To address this vulnerability, LibVNCClient should implement checks to reject Tight Gradient rectangles wider than 2048 pixels or replace the fixed-size buffers with dynamically sized allocations that are validated against safe limits.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed May 29, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-787 | Out-of-bounds Write | [email protected] |
Affected Products
No affected product data is available for this CVE.
Change History
5 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| May 29, 2026 | CVE Modified | CISA-ADP |
| May 28, 2026 | CVE Modified | CISA-ADP |
| May 27, 2026 | New CVE Received | [email protected] |