CVE-2019-7249 in Keybase
Summary
by MITRE
In Keybase before 2.12.6 on macOS, the move RPC to the Helper was susceptible to time-to-check-time-to-use bugs and would also allow one user of the system (who didn't have root access) to tamper with another's installs.
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Analysis
by VulDB Data Team • 07/04/2023
The vulnerability identified as CVE-2019-7249 represents a critical security flaw in Keybase client software versions prior to 2.12.6 on macOS platforms. This issue stems from improper handling of inter-process communication mechanisms within the application's architecture, specifically affecting the Helper component that manages privileged operations. The vulnerability creates a window of opportunity for malicious actors to exploit timing inconsistencies in the system's validation processes, allowing for unauthorized manipulation of installed components.
The technical implementation of this flaw manifests through time-to-check-time-to-use (TOCTOU) race conditions within the move RPC functionality. When Keybase attempts to move files or components to its Helper process, the system performs initial validation checks before executing the actual operation. However, between the time the check occurs and when the operation is completed, an attacker can manipulate the system state to alter the target files or directories. This creates a temporal gap where the system's assumptions about file integrity become invalid, enabling potential exploitation. The vulnerability is particularly concerning because it operates without requiring root privileges, making it accessible to regular users who would normally lack the elevated permissions necessary for such system-level modifications.
The operational impact of this vulnerability extends beyond simple privilege escalation as it enables a form of cross-user interference that violates fundamental security principles. An unprivileged user can potentially manipulate another user's Keybase installation by exploiting the race condition during file movement operations. This creates a scenario where one user's system integrity can be compromised by another user's actions, effectively breaking the isolation mechanisms that should protect individual user environments. The attack surface is further expanded because Keybase installations typically involve multiple components and services that may be manipulated through this vulnerability, potentially leading to complete system compromise or data exfiltration.
This vulnerability aligns with CWE-367, which specifically addresses Time-of-Check to Time-of-Use (TOCTOU) flaws, and demonstrates characteristics consistent with ATT&CK technique T1059.001 for command and scripting interpreter usage. The flaw represents a classic example of insufficient input validation combined with improper privilege management, where the application fails to properly secure its inter-process communication channels. Organizations using Keybase should consider this vulnerability as part of their broader security posture assessment, particularly in environments where multiple users share systems or where security isolation is critical. The remediation strategy involves updating to Keybase version 2.12.6 or later, which implements proper synchronization mechanisms and input validation to prevent the race conditions that enable this exploit. Additionally, system administrators should monitor for any signs of unauthorized modifications to Keybase installations and consider implementing additional access controls or monitoring solutions to detect potential exploitation attempts.
The broader implications of this vulnerability highlight the importance of robust security practices in client-side applications, particularly those that require elevated privileges for certain operations. The flaw demonstrates how seemingly minor implementation details in inter-process communication can create significant security risks, emphasizing the need for thorough security testing and validation of privileged code paths. Organizations should also consider the potential for similar vulnerabilities in other applications that rely on helper processes or privileged operations, as the underlying architectural patterns and race condition vulnerabilities are common across similar software ecosystems.