CVE-2013-1773 in Linux
Summary
by MITRE
Buffer overflow in the VFAT filesystem implementation in the Linux kernel before 3.3 allows local users to gain privileges or cause a denial of service (system crash) via a VFAT write operation on a filesystem with the utf8 mount option, which is not properly handled during UTF-8 to UTF-16 conversion.
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Analysis
by VulDB Data Team • 06/08/2024
The vulnerability identified as CVE-2013-1773 represents a critical buffer overflow flaw within the Linux kernel's VFAT filesystem implementation that affects versions prior to 3.3. This vulnerability specifically manifests when the VFAT filesystem is mounted with the utf8 option, which enables UTF-8 encoding for filename handling. The flaw stems from inadequate bounds checking during the conversion process between UTF-8 and UTF-16 character encodings, creating a condition where maliciously crafted data can exceed allocated buffer boundaries. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, which occurs when data is written beyond the allocated memory space, potentially leading to arbitrary code execution or system instability.
The technical exploitation of this vulnerability occurs during write operations on VFAT filesystems that utilize the utf8 mount option. When the kernel processes filename data that requires conversion from UTF-8 to UTF-16 encoding, the conversion routine fails to properly validate input length against buffer capacity. This allows an attacker to craft filenames or data structures that, when processed by the kernel's VFAT implementation, will overwrite adjacent memory locations. The buffer overflow can be triggered through normal filesystem write operations, making it particularly dangerous as it requires no special privileges beyond normal filesystem access. The vulnerability demonstrates characteristics consistent with ATT&CK technique T1068, which involves the exploitation of local privilege escalation opportunities through kernel-level flaws.
The operational impact of CVE-2013-1773 extends beyond simple denial of service to include potential privilege escalation capabilities that could allow local attackers to execute arbitrary code with kernel-level privileges. System crashes and instability represent the most immediate consequences, but the underlying buffer overflow condition creates opportunities for more sophisticated attacks where the attacker could overwrite critical kernel data structures or function pointers. This vulnerability particularly affects systems that utilize VFAT filesystems with UTF-8 support enabled, which is common in embedded systems, mobile devices, and various Linux distributions that support legacy filesystem compatibility. The attack vector is relatively straightforward since it only requires local access to perform write operations on the affected filesystem, making it a significant concern for systems where untrusted users might have filesystem access.
Mitigation strategies for CVE-2013-1773 primarily focus on upgrading to Linux kernel versions 3.3 or later where the vulnerability has been addressed through proper bounds checking and input validation in the VFAT filesystem implementation. System administrators should disable the utf8 mount option for VFAT filesystems when it is not strictly required, as this eliminates the vulnerable code path entirely. Additionally, implementing proper filesystem access controls and limiting local user privileges can reduce the attack surface for exploitation. The fix implemented in kernel version 3.3 includes enhanced validation routines that properly check buffer boundaries during UTF-8 to UTF-16 conversion processes, preventing the overflow condition that previously allowed attackers to manipulate kernel memory. Organizations should also consider monitoring filesystem write operations on VFAT partitions and implementing intrusion detection systems that can identify suspicious filename patterns that might indicate attempted exploitation of this vulnerability.