CVE-2021-38205 in Linux
Summary
by MITRE • 08/09/2021
drivers/net/ethernet/xilinx/xilinx_emaclite.c in the Linux kernel before 5.13.3 makes it easier for attackers to defeat an ASLR protection mechanism because it prints a kernel pointer (i.e., the real IOMEM pointer).
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Analysis
by VulDB Data Team • 08/14/2021
The vulnerability identified as CVE-2021-38205 resides within the Linux kernel's xilinx_emaclite network driver implementation, specifically in the drivers/net/ethernet/xilinx/xilinx_emaclite.c file. This flaw represents a significant security weakness that directly undermines the kernel's memory protection mechanisms. The vulnerability affects Linux kernel versions prior to 5.13.3, creating a persistent risk for systems utilizing Xilinx Ethernet MAC lite devices. The issue stems from the driver's improper handling of kernel pointer values during error reporting or debugging output operations, which exposes sensitive memory addresses to potential attackers.
The technical flaw manifests when the driver prints kernel pointers, specifically IOMEM pointers, to kernel log output or error messages. This behavior violates fundamental security principles by providing attackers with direct access to memory layout information that should remain obscured. The printed kernel pointers reveal the actual memory addresses of kernel structures, which are essential components for bypassing Address Space Layout Randomization protections. This exposure fundamentally undermines the effectiveness of ASLR, a critical defense mechanism designed to randomize memory locations and prevent exploitation of memory corruption vulnerabilities.
The operational impact of this vulnerability extends beyond simple information disclosure, as it significantly facilitates advanced exploitation techniques. Attackers can leverage the leaked kernel pointer information to craft more sophisticated attacks, particularly those involving return-oriented programming or jump-oriented programming techniques. The vulnerability creates opportunities for privilege escalation attacks where adversaries can use the disclosed memory addresses to bypass kernel protection mechanisms. This weakness is particularly dangerous in environments where multiple security mitigations are in place, as it provides attackers with the precise information needed to circumvent these protections. The vulnerability affects systems running affected kernel versions and is particularly concerning for embedded systems or network appliances that utilize Xilinx Ethernet MAC lite hardware components.
Mitigation strategies for CVE-2021-38205 primarily involve upgrading to Linux kernel version 5.13.3 or later, which contains the necessary patches to address the pointer disclosure issue. System administrators should prioritize kernel updates across all affected systems, particularly those handling sensitive network traffic or operating in security-critical environments. Additional defensive measures include implementing proper kernel log access controls to limit who can view kernel messages containing potentially sensitive information. The vulnerability aligns with CWE-200, which addresses information exposure, and represents a specific instance of improper information protection where kernel memory addresses are disclosed. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and defense evasion, as it enables attackers to bypass ASLR mechanisms that protect against exploitation. Organizations should also consider implementing monitoring for unusual kernel log patterns that might indicate exploitation attempts or information gathering activities targeting this specific vulnerability.