CVE-2014-0196 in Linux
Summary
by MITRE
The n_tty_write function in drivers/tty/n_tty.c in the Linux kernel through 3.14.3 does not properly manage tty driver access in the "LECHO & !OPOST" case, which allows local users to cause a denial of service (memory corruption and system crash) or gain privileges by triggering a race condition involving read and write operations with long strings.
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Analysis
by VulDB Data Team • 04/22/2026
The vulnerability identified as CVE-2014-0196 resides within the Linux kernel's terminal driver implementation, specifically in the n_tty_write function located in drivers/tty/n_tty.c. This flaw affects kernel versions through 3.14.3 and represents a critical race condition that can be exploited by local attackers to either crash the system or escalate privileges. The vulnerability stems from improper handling of tty driver access when the LECHO flag is set while OPOST is not set, creating a scenario where concurrent read and write operations can corrupt memory structures. The issue manifests when long strings are processed through the terminal subsystem, exploiting a timing window where the kernel fails to properly synchronize access to shared tty driver resources.
The technical exploitation of this vulnerability occurs through a race condition between read and write operations within the terminal driver context. When LECHO is enabled without OPOST, the kernel's n_tty_write function does not adequately protect against concurrent access patterns that can lead to memory corruption. This condition allows attackers to manipulate the tty driver state through carefully crafted input sequences that trigger the race condition. The flaw is categorized under CWE-362, which specifically addresses race conditions in concurrent systems, and aligns with ATT&CK technique T1068, which covers local privilege escalation through kernel vulnerabilities. The vulnerability enables an attacker to corrupt kernel memory structures, leading to unpredictable behavior including system crashes or privilege escalation to root level access.
The operational impact of CVE-2014-0196 extends beyond simple denial of service to encompass potential privilege escalation capabilities that can compromise entire systems. Local attackers who can execute code on a target system gain the ability to corrupt kernel memory through the race condition, potentially allowing them to execute arbitrary code with kernel privileges. This vulnerability affects systems running Linux kernel versions up to 3.14.3 and impacts any system utilizing the terminal subsystem with specific tty configuration settings. The memory corruption can result in immediate system crashes, making it a reliable vector for denial of service attacks, while the privilege escalation aspect provides attackers with persistent access to system resources. Systems with terminal access, particularly those running older kernel versions, face significant risk from this vulnerability.
Mitigation strategies for CVE-2014-0196 primarily involve updating to patched kernel versions where the race condition has been addressed through proper synchronization mechanisms. The fix implemented by kernel developers involves adding appropriate locking mechanisms to ensure that tty driver access is properly managed during read and write operations, particularly when LECHO is set without OPOST. Organizations should prioritize kernel updates to versions 3.14.4 and later, which contain the necessary patches to resolve this vulnerability. Additional defensive measures include monitoring for suspicious terminal activity and implementing proper access controls to limit local user privileges. System administrators should also consider disabling unnecessary terminal features and applying security hardening configurations that reduce the attack surface. The vulnerability demonstrates the importance of proper concurrent access control in kernel subsystems and highlights the need for comprehensive testing of race conditions in critical system components.