CVE-2010-5304: 
Linux Fedora vulnerability analysis and mitigation

A NULL pointer dereference vulnerability was discovered in LibVNCServer before version 0.9.9, identified as CVE-2010-5304. The vulnerability specifically affects how the server handles certain ClientCutText messages. This security issue was later found to also affect RealVNC VNC Server Free Edition (NVD, OSS Security).

The vulnerability stems from improper handling of ClientCutText messages in the VNC server implementation. When a malicious client sends a specially crafted ClientCutText message with a very large size (encoded as a 32-bit integer), the malloc() function is likely to fail. Due to insufficient checking of the malloc() return value, this leads to a NULL pointer dereference, ultimately resulting in a server crash (OSS Security).

The primary impact of this vulnerability is a denial of service condition. When successfully exploited, an attacker can cause the VNC server to crash by sending a specially crafted ClientCutText message (NVD).

The vulnerability requires authentication to exploit. However, it can still pose a significant security risk in scenarios where the VNC server is running in password-less mode (such as X11 login screens), when an attacker is in a man-in-the-middle position, or when an attacker has legitimate access to the VNC server but not to the host server (e.g., virtual machine, remote assistance scenarios) (OSS Security).

The vulnerability was addressed in LibVNCServer version 0.9.9. Users and administrators are advised to upgrade to this version or later to mitigate the security risk (NVD).