CVE-2016-10894 in xtrlock
Summary
by MITRE
xtrlock through 2.10 does not block multitouch events. Consequently, an attacker at a locked screen can send input to (and thus control) various programs such as Chromium via events such as pan scrolling, "pinch and zoom" gestures, or even regular mouse clicks (by depressing the touchpad once and then clicking with a different finger).
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Analysis
by VulDB Data Team • 11/26/2023
The vulnerability identified as CVE-2016-10894 affects xtrlock versions through 2.10, a screen locking utility designed to secure desktop environments by preventing unauthorized access when a system is locked. This flaw represents a critical security oversight in the implementation of input event handling during the locked state, fundamentally undermining the security assumptions that users rely upon when locking their systems. The vulnerability specifically targets the handling of multitouch events, which are commonly associated with touchpads and touchscreen interfaces found on modern laptops and hybrid devices. The absence of proper input filtering mechanisms allows malicious actors to bypass the screen lock protection through seemingly innocuous touch gestures that are typically intended for user interaction with applications.
The technical nature of this vulnerability stems from xtrlock's failure to properly intercept and block multitouch input events that occur while the screen is locked. When a user locks their system, the expectation is that all input devices will be effectively disabled or filtered to prevent any interaction with running applications. However, xtrlock's implementation does not adequately distinguish between legitimate lock screen events and potentially malicious input from multitouch gestures. This includes common touchpad interactions such as pan scrolling, pinch and zoom gestures, and even mouse click events that can be executed through touchpad depression followed by finger clicks on different locations. The vulnerability demonstrates a fundamental flaw in event handling architecture where the software fails to properly sanitize input streams, allowing touch-based interactions to propagate through to the underlying applications.
The operational impact of this vulnerability is significant as it provides attackers with a sophisticated method of maintaining access to locked systems without requiring direct authentication credentials or physical access to the device. An attacker positioned near a locked laptop can exploit this vulnerability to control applications running in the background, potentially accessing sensitive data, executing commands, or performing actions that could compromise system integrity. The specific attack vectors enabled by this vulnerability include the ability to manipulate web browsers like Chromium through touch gestures, which could lead to unauthorized navigation, data exfiltration, or exploitation of web-based vulnerabilities. This type of attack represents a sophisticated form of session hijacking that bypasses traditional security controls and can be executed without requiring specialized equipment or advanced technical skills.
The vulnerability aligns with CWE-254, which addresses security weaknesses related to improper input filtering, and demonstrates characteristics consistent with the ATT&CK framework's privilege escalation techniques. Specifically, this vulnerability enables an attacker to maintain persistent access to a system through input manipulation, potentially allowing for further exploitation and lateral movement within the network. The attack surface is particularly concerning given the prevalence of touch-enabled devices and the increasing reliance on touch-based interactions in modern computing environments. Organizations utilizing xtrlock for desktop security may be unknowingly exposing their systems to persistent threats that can be exploited by attackers with minimal resources. The vulnerability also highlights the importance of comprehensive input validation and filtering mechanisms in security-critical applications, particularly those designed to protect against unauthorized access and maintain system integrity. Mitigation strategies should include updating to patched versions of xtrlock, implementing additional input filtering mechanisms, and considering alternative screen locking solutions that properly handle multitouch event streams to prevent unauthorized access to locked systems.