CVE-2018-11412 in Linux
Summary
by MITRE
In the Linux kernel 4.13 through 4.16.11, ext4_read_inline_data() in fs/ext4/inline.c performs a memcpy with an untrusted length value in certain circumstances involving a crafted filesystem that stores the system.data extended attribute value in a dedicated inode.
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Analysis
by VulDB Data Team • 06/18/2024
The vulnerability identified as CVE-2018-11412 represents a critical buffer overflow flaw within the Linux kernel's ext4 filesystem implementation affecting versions 4.13 through 4.16.11. This issue stems from improper validation of extended attribute values during inline data reading operations, creating a potential avenue for arbitrary code execution or system compromise. The vulnerability specifically manifests in the ext4_read_inline_data() function located in fs/ext4/inline.c, where a memcpy operation utilizes an untrusted length parameter that can be manipulated through crafted filesystem structures. The attack vector requires a maliciously constructed filesystem with a specially crafted system.data extended attribute value stored in a dedicated inode, making this a sophisticated privilege escalation vulnerability that could be exploited by local attackers with write access to filesystem structures.
The technical exploitation of this vulnerability leverages the fundamental flaw in input validation where the kernel fails to properly sanitize the length parameter before performing memory copy operations. When the ext4 filesystem encounters a crafted extended attribute value, the system.data attribute can contain malicious data that influences the memcpy operation's parameters, leading to memory corruption. This type of vulnerability aligns with CWE-121, which categorizes buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations. The flaw demonstrates a classic case of inadequate input validation in kernel space, where trusted system components fail to validate untrusted data sources, creating a pathway for memory corruption that can be leveraged for privilege escalation or denial of service attacks.
The operational impact of CVE-2018-11412 extends beyond simple privilege escalation to encompass potential system instability and complete compromise of affected systems. An attacker with write access to a filesystem can construct malicious extended attribute values that trigger the vulnerable code path during read operations, potentially leading to kernel memory corruption and system crashes. This vulnerability affects systems running kernel versions within the specified range and impacts any application or service that relies on ext4 filesystem operations, particularly those handling untrusted filesystem data. The attack scenario typically requires local access to create or modify filesystem structures, but once exploited, could enable attackers to gain root privileges or cause system-wide denial of service conditions. The vulnerability's impact is further amplified by its potential to be chained with other exploits, as demonstrated in various exploit development frameworks that target similar kernel memory corruption vulnerabilities.
Mitigation strategies for CVE-2018-11412 primarily focus on kernel version updates and filesystem access controls to prevent exploitation. System administrators should immediately upgrade to kernel versions 4.16.12 or later where the vulnerability has been patched through proper bounds checking of extended attribute lengths. Additionally, implementing strict filesystem access controls and monitoring for unauthorized filesystem modifications can help detect potential exploitation attempts. The patch addresses the root cause by adding proper validation of the length parameter before the memcpy operation, ensuring that extended attribute values cannot exceed reasonable bounds. Organizations should also consider implementing runtime protections such as kernel address space layout randomization and stack canaries, although these provide limited protection against kernel-level buffer overflows. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques using kernel vulnerabilities and can be classified under T1068 for local privilege escalation, making it a critical target for both defensive and offensive security operations.