CVE-2017-14202 in Zephyr Shell
Summary
by MITRE
Improper Restriction of Operations within the Bounds of a Memory Buffer vulnerability in the shell component of Zephyr allows a serial or telnet connected user to cause a crash, possibly with arbitrary code execution. This issue affects: Zephyr shell versions prior to 1.14.0 on all.
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Analysis
by VulDB Data Team • 12/07/2023
The vulnerability identified as CVE-2017-14202 represents a critical memory safety issue within the Zephyr operating system's shell component that exposes systems to potential exploitation through improper bounds checking. This flaw exists in the shell subsystem responsible for handling serial and telnet connections, creating a pathway for authenticated attackers to manipulate memory operations beyond their intended boundaries. The vulnerability specifically impacts all versions of Zephyr shell prior to version 1.14.0, making it a widespread concern across numerous embedded systems and IoT devices that rely on this operating system framework.
The technical root cause of this vulnerability stems from inadequate input validation and memory boundary enforcement within the shell's command processing mechanisms. When users establish serial or telnet connections to systems running affected Zephyr versions, the shell component fails to properly validate the length and content of user-supplied commands before processing them. This allows maliciously crafted input to overwrite adjacent memory locations, potentially leading to stack corruption, heap manipulation, or other memory-related anomalies that can result in system instability. The vulnerability manifests as an improper restriction of operations within memory buffer boundaries, which aligns with CWE-121, which specifically addresses buffer overflow conditions where insufficient bounds checking allows access beyond allocated memory regions.
The operational impact of this vulnerability extends beyond simple system crashes to potentially enable arbitrary code execution, making it particularly dangerous for embedded environments where system integrity is paramount. An attacker with serial or telnet access can exploit this flaw to cause unpredictable behavior including system hangs, reboots, or more concerning unauthorized code execution that could compromise the entire device. The attack surface is significant since many embedded systems rely on serial and telnet interfaces for debugging, configuration, and remote management purposes, making these access points prime targets for exploitation. Systems utilizing Zephyr shell versions prior to 1.14.0 are particularly vulnerable as they lack the memory safety improvements implemented in later releases.
Mitigation strategies for this vulnerability require immediate action to upgrade affected systems to Zephyr shell version 1.14.0 or later, which incorporates proper bounds checking and input validation mechanisms. Organizations should also implement network segmentation to limit access to serial and telnet interfaces, particularly in production environments where such access should be restricted to authorized personnel only. Additional defensive measures include implementing strict input filtering and validation at all entry points, monitoring for anomalous command sequences, and maintaining comprehensive system logging to detect potential exploitation attempts. From a cybersecurity perspective, this vulnerability maps to ATT&CK technique T1059.007 for Command and Scripting Interpreter and T1068 for Exploitation for Privilege Escalation, highlighting the multi-faceted nature of the threat. The remediation process should also include thorough security testing of all shell components, particularly focusing on memory handling and boundary validation, to ensure that similar vulnerabilities are not present in other parts of the system architecture.