CVE-2016-5407 in Secure Global Desktop
Summary
by MITRE
The (1) XvQueryAdaptors and (2) XvQueryEncodings functions in X.org libXv before 1.0.11 allow remote X servers to trigger out-of-bounds memory access operations via vectors involving length specifications in received data.
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Analysis
by VulDB Data Team • 12/01/2022
The vulnerability identified as CVE-2016-5407 affects the X.org libXv library version 1.0.10 and earlier, representing a critical memory safety issue within the X Window System's video extension implementation. This flaw manifests in two distinct functions: XvQueryAdaptors and XvQueryEncodings, which are responsible for querying video adaptor information and encoding capabilities respectively. The vulnerability stems from insufficient input validation mechanisms that fail to properly sanitize length specifications contained within received data packets from remote X servers. When these functions process malformed data containing excessive or negative length values, they proceed to allocate memory buffers based on these unvalidated parameters without adequate bounds checking.
The technical exploitation of this vulnerability occurs when a remote attacker establishes a connection to an X server running an affected version of libXv and sends specially crafted X protocol requests containing malformed length fields. These requests trigger out-of-bounds memory access operations as the functions attempt to process data structures using invalid memory offsets or buffer sizes. The flaw aligns with CWE-129, which specifically addresses insufficient validation of length parameters, and represents a classic case of buffer over-read conditions that can lead to memory corruption. The X protocol's design allows for remote communication between X servers and clients, making this vulnerability particularly dangerous as it can be exploited from external networks without requiring local access to the target system.
The operational impact of CVE-2016-5407 extends beyond simple memory corruption, as it can potentially enable remote code execution or denial of service conditions depending on the specific memory layout and the attacker's control over the data flow. When exploited successfully, the vulnerability can cause application crashes, data corruption, or in more sophisticated attacks, arbitrary code execution within the context of the X server process. This represents a significant threat to graphical environments, particularly in multi-user systems where X server instances may be accessible to untrusted network clients. The vulnerability affects systems running X.org versions prior to 1.0.11 and impacts desktop environments, remote desktop solutions, and any application relying on the X Window System's video extension functionality.
Mitigation strategies for this vulnerability primarily focus on immediate patching of the affected libXv library to version 1.0.11 or later, which includes proper input validation and bounds checking mechanisms. System administrators should also implement network segmentation to limit access to X servers and consider disabling unnecessary X11 forwarding capabilities in SSH configurations. Additional protective measures include implementing X server access controls through xhost and host-based authentication mechanisms, as well as monitoring for suspicious X protocol traffic patterns. The ATT&CK framework categorizes this vulnerability under T1190 - Exploit Public-Facing Application, as it represents an attack vector that targets publicly accessible X server services. Organizations should also consider implementing intrusion detection systems capable of identifying malformed X protocol packets and establishing regular vulnerability assessment procedures to identify and remediate similar issues in other components of their X Window System infrastructure.