CVE-2017-12762 in Linux
Summary
by MITRE • 01/25/2023
In /drivers/isdn/i4l/isdn_net.c: A user-controlled buffer is copied into a local buffer of constant size using strcpy without a length check which can cause a buffer overflow. This affects the Linux kernel 4.9-stable tree, 4.12-stable tree, 3.18-stable tree, and 4.4-stable tree.
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Analysis
by VulDB Data Team • 01/25/2023
The vulnerability identified as CVE-2017-12762 represents a classic buffer overflow flaw within the Linux kernel's ISDN (Integrated Services Digital Network) subsystem, specifically in the isdn_net.c driver file. This issue resides in the kernel's handling of network interface operations for ISDN connections, where user-supplied data is processed through an unsafe string copying mechanism. The flaw affects multiple stable kernel release branches including 4.9, 4.12, 3.18, and 4.4, indicating a widespread impact across various kernel versions that have been in production use for extended periods.
The technical implementation of this vulnerability stems from the improper use of the strcpy function without any bounds checking against a fixed-size local buffer. When user-controlled data is passed through the ISDN network driver, the code assumes the input will fit within the predetermined buffer space without validating the actual data length. This fundamental flaw creates an exploitable condition where an attacker can craft malicious input that exceeds the buffer capacity, leading to memory corruption that can overwrite adjacent memory locations. The vulnerability is categorized under CWE-121 as a stack-based buffer overflow, which represents one of the most dangerous types of buffer overflow conditions due to its potential for arbitrary code execution.
The operational impact of this vulnerability extends beyond simple memory corruption, as it provides potential attackers with a pathway for privilege escalation within the kernel space. Since the affected driver operates within the kernel context, successful exploitation could allow an attacker to execute arbitrary code with the highest privileges available to the kernel, potentially leading to complete system compromise. The vulnerability affects systems running the affected kernel versions where ISDN networking is enabled, making it particularly concerning for enterprise environments that rely on legacy ISDN infrastructure or systems where the ISDN driver module remains loaded. The exploitation of this condition aligns with ATT&CK technique T1068 which describes "Exploitation for Privilege Escalation" and could be leveraged as part of broader attack chains targeting kernel-level vulnerabilities.
Mitigation strategies for CVE-2017-12762 primarily focus on immediate kernel updates to versions that have patched the vulnerable code path, as the official fix involves implementing proper bounds checking before buffer copying operations. System administrators should prioritize updating to kernel versions that contain the appropriate patches, typically found in the 4.13 and later stable releases. Additionally, organizations should consider disabling the ISDN subsystem entirely if it is not actively required, as this reduces the attack surface and eliminates the risk associated with this particular vulnerability. The patch implementation should follow standard security hardening practices and include thorough regression testing to ensure that legitimate ISDN functionality remains intact while addressing the buffer overflow condition. Organizations utilizing older kernel versions that cannot be immediately updated should implement network segmentation and access controls to limit potential exploitation vectors and monitor for suspicious network activity that might indicate attempted exploitation of this vulnerability.