Buffer Overflow Vulnerability in LibVNCClient Affects Multiple Versions

CVE-2026-44988

What is CVE-2026-44988?

LibVNCClient is a widely used library for implementing VNC clients. Versions 0.9.15 and earlier include a vulnerability where the Tight encoding decoder utilizes fixed-size 2048-pixel scratch buffers for the Gradient filter without properly validating the dimensions of the incoming Tight rectangles. A malicious VNC server can exploit this weakness by sending specially crafted FramebufferUpdate rectangles that exceed the fixed buffer sizes, leading to a buffer overflow when processed by a LibVNCClient-based client. This flaw has been addressed with specific code changes, enhancing the security of the library.

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