CVE-2016-7948 in libXrandr
Summary
by MITRE
X.org libXrandr before 1.5.1 allows remote X servers to trigger out-of-bounds write operations by leveraging mishandling of reply data.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 09/22/2022
The vulnerability identified as CVE-2016-7948 affects the X.org libXrandr library version 1.5.1 and earlier, representing a critical security flaw that enables remote attackers to execute out-of-bounds write operations against X server implementations. This vulnerability resides within the X Window System protocol handling mechanisms, specifically targeting how the library processes reply data from X server communications. The flaw occurs when the libXrandr library fails to properly validate or sanitize data received in response to X protocol requests, creating opportunities for malicious actors to manipulate memory operations through crafted server responses.
The technical implementation of this vulnerability stems from improper bounds checking within the X protocol reply processing code, which falls under CWE-129 Input Validation and CWE-787 Out-of-bounds Write. When an X server sends a reply containing malformed or oversized data structures, the libXrandr library does not adequately verify the data boundaries before attempting to write to memory locations. This mismanagement creates a scenario where attacker-controlled data can overwrite adjacent memory regions, potentially leading to arbitrary code execution or system instability. The vulnerability specifically impacts the X11 RandR extension which handles display configuration and resolution changes, making it particularly dangerous in graphical environments where multiple applications interact with X server components.
Operationally, this vulnerability poses significant risks to systems relying on X Window System implementations, particularly in server environments, remote desktop solutions, and any application that utilizes libXrandr for display management. An attacker could exploit this vulnerability by establishing a connection to a vulnerable X server and sending specially crafted reply data that triggers the out-of-bounds write condition. The impact extends beyond simple denial of service, as successful exploitation could lead to privilege escalation, arbitrary code execution, or complete system compromise depending on the execution environment and privileges of the affected X server process. The remote nature of the attack means that systems are vulnerable even when behind firewalls or network segmentation, as long as the X server accepts connections from untrusted sources.
Mitigation strategies for CVE-2016-7948 primarily focus on immediate patching of affected libXrandr versions, with the recommended upgrade to version 1.5.1 or later where the vulnerability has been addressed through proper bounds checking implementation. Organizations should also implement network segmentation to restrict access to X servers, disable unnecessary X11 forwarding capabilities, and employ firewall rules to limit X server connections to trusted hosts only. Additionally, monitoring for unusual X server activity and implementing intrusion detection systems can help identify potential exploitation attempts. The vulnerability aligns with ATT&CK technique T1059 Command and Scripting Interpreter and T1203 Exploitation for Client Execution, as it represents a classic remote code execution vector that can be leveraged for broader system compromise. System administrators should also consider implementing the principle of least privilege for X server processes and regularly audit X server configurations to minimize attack surface.