A vulnerability in the Virtual Network Computing (VNC) server implementation in Quick Emulator (QEMU) could allow an authenticated, remote attacker to cause a denial of service (DoS) condition on a targeted system.
The vulnerability exists because the VNC server integrated with the affected software improperly restricts memory allocation when sending framebuffer updates to VNC clients. An attacker on a VNC client could exploit this vulnerability by blocking framebuffer updates sent from a targeted VNC host system. A successful exploit could cause the host system to allocate more memory to hold the update data, which could cause a DoS condition.
QEMU has confirmed the vulnerability and released software updates.
To exploit this vulnerability, an attacker must have user-level access to a VNC client system to block framebuffer updates sent from a targeted VNC host system. This access requirement may reduce the likelihood of a successful exploit.
Administrators are advised to apply the appropriate updates.
Administrators are advised to allow only trusted users to have network access.
Administrators are advised to run both firewall and antivirus applications to minimize the potential of inbound and outbound threats.
Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.
Administrators can help protect affected systems from external attacks by using a solid firewall strategy.
Administrators are advised to monitor affected systems.
QEMU has released a security announcement at the following link: msg0705
QEMU has released software patches at the following links:
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Cisco Multivendor Vulnerability Alerts respond to vulnerabilities identified in third-party vendors' products. These alerts contain information compiled from diverse sources and provide comprehensive technical descriptions, objective analytical assessments, workarounds and practical safeguards, and links to vendor advisories and patches.