CVE-2020-13143 in Linux
Summary
by MITRE
gadget_dev_desc_UDC_store in drivers/usb/gadget/configfs.c in the Linux kernel through 5.6.13 relies on kstrdup without considering the possibility of an internal '\0' value, which allows attackers to trigger an out-of-bounds read, aka CID-15753588bcd4.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 10/18/2020
The vulnerability identified as CVE-2020-13143 resides within the Linux kernel's USB gadget framework, specifically in the gadget_dev_desc_UDC_store function located in drivers/usb/gadget/configfs.c. This flaw affects Linux kernel versions through 5.6.13 and represents a critical security issue that stems from improper handling of string data during USB device descriptor configuration. The vulnerability manifests when the kernel processes USB gadget device descriptions through the configfs interface, which provides a userspace interface for configuring USB gadgets.
The technical root cause of this vulnerability lies in the function's reliance on kstrdup without proper validation of the input string for null byte characters. When an attacker supplies a string containing an internal null character, the function fails to handle this condition appropriately, leading to improper memory handling and subsequent out-of-bounds read operations. This behavior violates fundamental security principles regarding input validation and memory safety, as the function does not account for the possibility that user-provided strings might contain embedded null terminators that could disrupt normal string processing operations. The vulnerability is classified under CWE-125 as an out-of-bounds read, which occurs when the kernel attempts to access memory beyond the bounds of allocated buffers.
The operational impact of this vulnerability is significant as it can be exploited by malicious actors to gain unauthorized access to kernel memory regions, potentially leading to information disclosure or privilege escalation. Attackers can craft specially formatted USB gadget device descriptions containing embedded null characters to trigger the out-of-bounds read condition. This vulnerability falls under the ATT&CK technique T1068 for locally executed malicious code and could be leveraged in kernel-level attacks. The vulnerability is particularly concerning because it exists within the USB gadget subsystem, which is commonly used in embedded systems, network infrastructure devices, and various hardware platforms that rely on Linux kernel USB functionality. An attacker could exploit this vulnerability to read sensitive kernel memory contents, potentially exposing confidential information, kernel addresses, or other critical system data.
Mitigation strategies for CVE-2020-13143 should prioritize applying the official kernel patches released by the Linux kernel security team, which address the improper string handling by implementing proper validation of input strings before processing. System administrators should ensure all affected systems are updated to kernel versions containing the fix, typically kernel 5.6.14 or later. Additionally, organizations should implement monitoring for suspicious USB gadget configuration activities and consider restricting access to the configfs interface where possible. The vulnerability demonstrates the importance of robust input validation in kernel space code and highlights the need for thorough testing of string handling functions. Security teams should also consider implementing kernel memory protection mechanisms such as stack canaries, kernel address space layout randomization, and other exploit mitigation techniques to reduce the potential impact of similar vulnerabilities. The fix typically involves modifying the gadget_dev_desc_UDC_store function to properly validate input strings and prevent the propagation of embedded null characters that could lead to memory corruption issues.