CVE-2022-3239 in Linux
Summary
by MITRE • 09/20/2022
A flaw use after free in the Linux kernel video4linux driver was found in the way user triggers em28xx_usb_probe() for the Empia 28xx based TV cards. A local user could use this flaw to crash the system or potentially escalate their privileges on the system.
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Analysis
by VulDB Data Team • 10/20/2022
The vulnerability identified as CVE-2022-3239 represents a critical use-after-free flaw within the Linux kernel's video4linux driver subsystem, specifically affecting the em28xx_usb_probe() function that handles Empia 28xx based TV cards. This type of vulnerability occurs when a program continues to reference memory after it has been freed, creating a dangerous condition that can be exploited by malicious actors. The flaw exists in the kernel's handling of USB device probe operations for specific video capture hardware, making it particularly concerning for systems that utilize these particular TV card models.
The technical implementation of this vulnerability stems from improper memory management within the em28xx driver module, where the em28xx_usb_probe() function fails to properly validate or manage memory references during device initialization. When a local user triggers this probe function through specific USB device interactions, the kernel allocates memory structures that are subsequently freed but not properly nullified or validated before being accessed again. This memory management error creates a window where an attacker can manipulate the system's memory state to either cause a denial of service through system crashes or potentially execute code with elevated privileges. The vulnerability is classified under CWE-416 as a use-after-free condition, which is a well-known category of memory safety issues that frequently leads to privilege escalation exploits.
The operational impact of this vulnerability extends beyond simple system instability, as it provides a pathway for local privilege escalation attacks that can compromise the entire system. A local user who can successfully trigger the vulnerable code path gains the ability to either crash the kernel through controlled memory access violations or potentially execute arbitrary code with kernel-level privileges. This represents a significant security risk in environments where untrusted users have access to systems running affected kernel versions. The attack vector requires local system access but does not necessitate network connectivity, making it particularly dangerous in multi-user environments or systems where user isolation is not properly enforced.
Mitigation strategies for CVE-2022-3239 should focus on immediate kernel updates and patches provided by the Linux kernel security team, which typically address the memory management issues through proper nullification of freed pointers and enhanced validation routines. System administrators should prioritize applying the relevant security patches as soon as they become available, as the vulnerability can be exploited by any local user with sufficient privileges to interact with the affected USB device drivers. Additional defensive measures include implementing proper kernel lockdown mechanisms, restricting local user access to USB device interfaces, and monitoring for unusual kernel memory access patterns. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation through kernel exploits and can be categorized under T1068 for local privilege escalation, making it a critical target for security hardening efforts and vulnerability management programs.