CVE-2023-4273
Linux Kernel vulnerability analysis and mitigation

Overview

A vulnerability (CVE-2023-4273) was discovered in the exFAT driver of the Linux kernel. The flaw exists in the implementation of the file name reconstruction function, which is responsible for reading file name entries from a directory index and merging file name parts belonging to one file into a single long file name. The vulnerability was discovered by Maxim Suhanov and disclosed on August 9, 2023. The issue affects Linux kernel versions prior to 6.5-rc5 (NVD, DFIR Blog).

Technical details

The vulnerability stems from improper handling of file name length limits in the exFAT driver. While the exFAT specification limits file names to 255 characters (UTF-16LE), this limit wasn't properly enforced in the Linux kernel implementation. The flaw allows crafting a File directory entry set containing more than 17 File Name directory entries, resulting in a concatenated file name longer than the allowed limit. These characters are copied into a stack-allocated array of 258 characters, leading to a stack overflow. The maximum overflow can reach 7104 bytes (38102-2582 bytes) (DFIR Blog). The vulnerability has been assigned a CVSS v3.1 base score of 6.7 MEDIUM (AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H) (NVD).

Impact

When successfully exploited, this vulnerability could allow a local privileged attacker to overflow the kernel stack. The impact includes potential denial of service through system crashes and possible privilege escalation. The vulnerability is particularly concerning as it can potentially bypass stack canaries and could be used to disable certain kernel protection mechanisms like the lockdown mode (DFIR Blog).

Mitigation and workarounds

The vulnerability has been fixed in Linux kernel version 6.5-rc5. Various Linux distributions have released security updates to address this issue, including Red Hat Enterprise Linux 9 via RHSA-2023:6583, Debian 11 (Bullseye) in version 5.10.191-1, and Debian 12 (Bookworm) in version 6.1.52-1 (Red Hat Advisory, Debian Advisory).

Additional resources


SourceThis report was generated using AI

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