CVE-2019-14201 in Das U-Boot
Summary
by MITRE
An issue was discovered in Das U-Boot through 2019.07. There is a stack-based buffer overflow in this nfs_handler reply helper function: nfs_lookup_reply.
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Analysis
by VulDB Data Team • 11/14/2023
The vulnerability identified as CVE-2019-14201 resides within Das U-Boot, a widely used open source bootloader that serves as the foundation for numerous embedded systems and network appliances. This critical flaw manifests in the nfs_lookup_reply function, which is part of the network file system handler component. The issue represents a classic stack-based buffer overflow that occurs when processing network file system responses, specifically during the lookup operation that occurs when the bootloader attempts to resolve network file system paths. Such vulnerabilities are particularly dangerous in embedded environments where the bootloader operates with high privileges and controls system initialization.
The technical implementation of this vulnerability stems from inadequate input validation within the nfs_lookup_reply helper function. When the U-Boot bootloader receives a network file system response containing a lookup reply, it fails to properly bounds-check the incoming data before copying it into a fixed-size stack buffer. This allows an attacker positioned on the network to craft malicious NFS responses that exceed the buffer capacity, resulting in memory corruption that can overwrite adjacent stack variables, return addresses, and potentially execute arbitrary code. The flaw directly maps to CWE-121 Stack-based Buffer Overflow, which is categorized under the broader weakness of insufficient boundary checking in memory management operations.
The operational impact of this vulnerability extends far beyond simple denial of service scenarios, as it creates a potential pathway for remote code execution within the bootloader environment. Attackers capable of intercepting network traffic or positioning themselves within the network segment can exploit this vulnerability to gain control over devices running affected U-Boot versions. This is particularly concerning given that U-Boot is deployed in critical infrastructure devices including routers, switches, embedded servers, and IoT devices where the bootloader represents the first line of system security. The vulnerability affects all versions through 2019.07, indicating a significant window of exposure where numerous production devices may remain vulnerable. The ATT&CK framework categorizes this as a privilege escalation technique through exploitation of software vulnerabilities, potentially enabling attackers to move laterally within network environments or establish persistent access points.
Mitigation strategies for CVE-2019-14201 primarily focus on immediate firmware updates from device vendors who have patched this vulnerability in their U-Boot implementations. Organizations should prioritize updating their embedded systems to versions containing the patched nfs_lookup_reply function, which typically involves implementing proper bounds checking and input validation before buffer operations. Network segmentation and monitoring can provide additional defensive layers by limiting the attack surface and detecting anomalous NFS traffic patterns that might indicate exploitation attempts. The vulnerability highlights the importance of robust input validation in embedded systems and demonstrates how seemingly minor flaws in bootloader components can have cascading security implications throughout entire device ecosystems. Security teams should also consider implementing network access controls and firewall rules to restrict NFS traffic to trusted network segments, reducing the likelihood of exploitation from external attackers.