CVE-2017-7273 in Linux
Summary
by MITRE
The cp_report_fixup function in drivers/hid/hid-cypress.c in the Linux kernel 4.x before 4.9.4 allows physically proximate attackers to cause a denial of service (integer underflow) or possibly have unspecified other impact via a crafted HID report.
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Analysis
by VulDB Data Team • 11/22/2022
The vulnerability identified as CVE-2017-7273 resides within the Linux kernel's HID (Human Interface Device) subsystem, specifically in the cp_report_fixup function located in drivers/hid/hid-cypress.c. This flaw affects Linux kernel versions 4.x prior to 4.9.4 and represents a critical security issue that can be exploited by attackers who are physically present near the target system. The vulnerability stems from improper input validation within the HID report processing logic, creating a scenario where maliciously crafted HID reports can trigger unexpected behavior in the kernel's device handling mechanisms.
The technical implementation of this vulnerability involves an integer underflow condition that occurs when the cp_report_fixup function processes specially crafted HID reports. This function is responsible for fixing up HID report descriptors for Cypress HID devices, but fails to properly validate the length parameters of incoming reports. When an attacker sends a HID report with a malformed length field, the function performs arithmetic operations that result in integer underflow, causing the kernel to behave unpredictably. This condition can lead to kernel memory corruption, system instability, and ultimately a denial of service condition where the affected system becomes unresponsive or crashes entirely.
The operational impact of this vulnerability extends beyond simple denial of service, as the integer underflow condition may potentially enable more sophisticated attacks depending on the execution context. An attacker with physical proximity can exploit this vulnerability to disrupt system operations, making it particularly dangerous in environments where physical access control is insufficient or compromised. The vulnerability affects systems using Cypress HID devices such as keyboards, mice, and other input peripherals that rely on the affected kernel version. From a cybersecurity perspective, this vulnerability aligns with CWE-191, which specifically addresses integer underflow conditions, and represents a classic example of a buffer manipulation flaw that can be leveraged for privilege escalation or system compromise.
Mitigation strategies for CVE-2017-7273 primarily involve upgrading to Linux kernel version 4.9.4 or later, which contains the necessary patches to address the integer underflow condition in the cp_report_fixup function. System administrators should prioritize this upgrade across all affected systems, particularly those in high-security environments or critical infrastructure deployments. Additionally, implementing proper input validation and sanitization measures within HID processing code can provide defense-in-depth protection against similar vulnerabilities. Network segmentation and physical access controls should remain in place to limit potential attack vectors, while monitoring systems should be configured to detect unusual HID report patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of thorough input validation in kernel space code and highlights the need for comprehensive security testing of device drivers, particularly those handling external input devices that may be subject to physical attack scenarios.