CVE-2024-25941 in FreeBSD
Summary
by MITRE • 02/15/2024
The jail(2) system call has not limited a visiblity of allocated TTYs (the kern.ttys sysctl). This gives rise to an information leak about processes outside the current jail. Attacker can get information about TTYs allocated on the host or in other jails. Effectively, the information printed by "pstat -t" may be leaked.
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Analysis
by VulDB Data Team • 11/20/2024
The vulnerability identified as CVE-2024-25941 resides within the FreeBSD operating system's jail implementation and specifically targets the jail system call functionality. This flaw represents a significant information disclosure issue that undermines the fundamental security isolation principles that jails are designed to enforce. The vulnerability manifests through improper handling of TTY (teletypewriter) visibility controls within the kernel's tty subsystem, creating a pathway for unauthorized information leakage between different security contexts. The issue stems from the kern.ttys sysctl parameter not properly enforcing visibility restrictions when processes operate within jailed environments, thereby allowing processes to access TTY information that should remain isolated within their respective security boundaries.
The technical implementation flaw occurs at the kernel level where the jail(2) system call fails to properly restrict TTY visibility controls. When a process executes within a jail environment, the system should normally prevent access to TTY devices and associated information that belongs to the host system or other jails. However, due to this vulnerability, processes within a jail can enumerate and potentially access TTY information from the host system or other jail environments. This creates a direct information leakage channel that bypasses normal security boundaries, effectively undermining the isolation properties that make jails useful for security separation. The vulnerability specifically affects the tty subsystem's handling of the kern.ttys parameter, which controls the visibility and accessibility of terminal devices across different system contexts.
The operational impact of CVE-2024-25941 extends beyond simple information disclosure, as it can enable more sophisticated attacks that leverage the leaked TTY information for further exploitation. An attacker who successfully exploits this vulnerability can gain insights into running processes, their terminal associations, and potentially the underlying system configuration. The specific information leak demonstrated by the ability to access "pstat -t" output means that attackers can discover which processes are connected to which terminals, potentially identifying sensitive processes or services that might be targeted in subsequent attacks. This information can be particularly valuable for attackers planning privilege escalation or lateral movement attacks, as terminal associations often correlate with process privileges and system roles.
The vulnerability aligns with CWE-200, which addresses "Information Exposure," and represents a classic case of insufficient access control within a security boundary. From an ATT&CK framework perspective, this vulnerability maps to techniques involving information gathering and reconnaissance activities, specifically T1082 for system information discovery and T1592 for reconnaissance. The flaw essentially creates a covert channel through which attackers can perform reconnaissance without direct interaction with the target system, making detection more difficult. Organizations running FreeBSD systems with jail functionality are particularly at risk, as this vulnerability can be exploited by any user with access to a jail environment to gain unauthorized visibility into the broader system. The impact is particularly concerning in multi-tenant environments where multiple users operate within isolated jail contexts, as it can enable cross-tenant information leakage and potentially compromise the security of other users on the same host.
Mitigation strategies for CVE-2024-25941 should focus on both immediate system hardening and long-term architectural improvements. System administrators should ensure that FreeBSD systems are updated with the latest security patches as soon as they become available, as this vulnerability represents a clear security risk that can be exploited by malicious actors. The recommended approach involves implementing proper TTY visibility controls within jail environments and ensuring that the kern.ttys sysctl parameter properly enforces access restrictions. Additionally, organizations should consider implementing monitoring solutions that can detect anomalous TTY enumeration activities, particularly in environments where jail functionality is used. Network segmentation and access control policies should also be reviewed to limit the potential impact of information leakage. The vulnerability highlights the importance of maintaining up-to-date security configurations and proper system hardening practices, as well as the need for regular security assessments of system call interfaces and kernel functionality.