Heap Buffer Overflow in GStreamer rfbsrc Plugin

Executive Summary

CVE-2026-59691 is a heap buffer overflow vulnerability found in GStreamer's rfbsrc plugin, specifically in the function that processes Hextile-encoded updates from RFB/VNC servers.

When a client connects to a malicious RFB/VNC server that advertises a 16 bits-per-pixel (bpp) framebuffer, the plugin incorrectly writes 32-bit pixel values into a buffer allocated for 16-bit pixels. This mismatch causes an out-of-bounds write on the heap.

The flaw occurs because the decoder calculates the destination offset assuming 2 bytes per pixel but writes 4 bytes per pixel, leading to heap corruption.

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Impact Analysis

This vulnerability can lead to denial of service by causing the affected process to crash due to heap corruption.

While remote code execution has not been demonstrated, the heap buffer overflow could potentially be exploited to corrupt memory, which might lead to further security issues.

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Detection Guidance

This vulnerability occurs when a client using GStreamer's rfbsrc plugin connects to a malicious RFB/VNC server that advertises a 16bpp framebuffer and sends Hextile-encoded updates. Detection involves monitoring for connections to suspicious or untrusted RFB/VNC servers and analyzing the behavior of the rfbsrc plugin during such connections.

Since the vulnerability triggers a heap buffer overflow in the rfbsrc plugin, signs of exploitation may include process crashes or abnormal termination of applications using GStreamer with the rfbsrc plugin.

There are no specific commands provided in the resources to detect this vulnerability directly. However, you can monitor network connections to RFB/VNC servers and check logs for crashes related to GStreamer or rfbsrc.

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Mitigation Strategies

Immediate mitigation steps include avoiding connecting to untrusted or malicious RFB/VNC servers using the GStreamer rfbsrc plugin.

Update GStreamer gst-plugins-bad to version 1.28.5 or later, where the fix for this vulnerability has been planned and merged.

If updating is not immediately possible, consider disabling or restricting the use of the rfbsrc plugin to prevent exploitation.

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Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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