CVE-2022-46340 in X11 Server
Summary
by MITRE • 12/15/2022
A vulnerability was found in X.Org. This security flaw occurs becuase the swap handler for the XTestFakeInput request of the XTest extension may corrupt the stack if GenericEvents with lengths larger than 32 bytes are sent through a the XTestFakeInput request. This issue can lead to local privileges elevation on systems where the X server is running privileged and remote code execution for ssh X forwarding sessions. This issue does not affect systems where client and server use the same byte order.
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Analysis
by VulDB Data Team • 11/15/2024
The vulnerability identified as CVE-2022-46340 represents a critical stack corruption flaw within the X.Org X server implementation that affects the XTest extension's swap handler functionality. This security weakness specifically manifests when processing GenericEvents through the XTestFakeInput request where event lengths exceed 32 bytes, creating a potential pathway for privilege escalation and remote code execution. The flaw resides in the X server's handling of event data structures during the swap operation process, which occurs when events are processed across different byte order boundaries.
The technical exploitation of this vulnerability stems from improper boundary checking within the XTest extension's event processing logic. When GenericEvents with payloads larger than 32 bytes are transmitted via XTestFakeInput, the swap handler fails to properly validate the event length against the expected buffer size, leading to stack buffer overflow conditions. This improper memory management creates opportunities for attackers to manipulate stack contents and potentially execute arbitrary code with the privileges of the X server process. The vulnerability operates under CWE-121, which addresses stack-based buffer overflow conditions, and aligns with ATT&CK technique T1068 for privilege escalation through local exploitation.
The operational impact of CVE-2022-46340 extends across multiple attack vectors and system configurations. Local privilege escalation becomes possible on systems where the X server runs with elevated privileges, allowing attackers to gain root access or higher-level permissions. Additionally, the vulnerability enables remote code execution in SSH X forwarding sessions, where attackers can exploit the flaw through network-based connections to compromise systems. The attack surface is particularly concerning for enterprise environments where X11 forwarding is commonly used for remote desktop access and application delivery. However, systems where client and server operate with identical byte order configurations remain unaffected by this vulnerability, as the swap handling process is bypassed in these scenarios.
Mitigation strategies for CVE-2022-46340 should prioritize immediate patch deployment from X.Org and system administrators should implement comprehensive monitoring for suspicious X server activity. The recommended approach includes applying the vendor-provided security patches that address the stack corruption handling within the XTest extension's swap routines. Organizations should also consider implementing network segmentation to limit exposure of X server processes and disable unnecessary X11 forwarding capabilities where possible. Security controls should focus on monitoring for abnormal event processing patterns and implementing strict access controls for X server connections. System hardening measures including disabling unnecessary X extensions and employing privilege separation techniques can further reduce the attack surface. The vulnerability demonstrates the critical importance of proper input validation and memory boundary checking in server-side applications, particularly those handling untrusted event data from remote clients.