CVE-2018-11020 in Kindle Fire HD
Summary
by MITRE
kernel/omap/drivers/rpmsg/rpmsg_omx.c in the kernel component in Amazon Kindle Fire HD(3rd) Fire OS 4.5.5.3 allows attackers to inject a crafted argument via the argument of an ioctl on device file /dev/rpmsg-omx1 with the command 3221772291, and cause a kernel crash.
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Analysis
by VulDB Data Team • 04/02/2020
The vulnerability identified as CVE-2018-11020 resides within the Linux kernel's rpmsg_omx driver component, specifically in the kernel/omap/drivers/rpmsg/rpmsg_omx.c file. This flaw affects Amazon Kindle Fire HD (3rd generation) devices running Fire OS 4.5.5.3, representing a critical security issue that stems from improper input validation within the kernel space. The vulnerability manifests through a privilege escalation path via a malicious ioctl command execution, where attackers can manipulate device file operations to trigger kernel-level crashes.
The technical implementation of this vulnerability involves a specific ioctl command with the value 3221772291 being executed against the /dev/rpmsg-omx1 device file. This command triggers a kernel memory corruption condition that results in a kernel crash, effectively causing a denial of service condition. The flaw demonstrates a classic buffer overflow or argument injection vulnerability where the kernel fails to properly validate or sanitize the input arguments passed to the ioctl handler. According to CWE classification, this corresponds to CWE-121: Stack-based Buffer Overflow, as the vulnerability involves improper handling of user-supplied data within kernel memory space. The attack vector requires local access to the device, as the vulnerability is triggered through direct interaction with the device file interface.
From an operational impact perspective, this vulnerability represents a significant risk to device stability and user experience, as it can be exploited to cause unexpected system crashes and restarts. The kernel crash resulting from this vulnerability effectively renders the device temporarily unusable until a reboot occurs, potentially disrupting critical user activities. The exploitation of this vulnerability aligns with ATT&CK technique T1068: Exploitation for Privilege Escalation, as the kernel-level memory corruption allows attackers to potentially gain elevated privileges within the device's operating environment. The impact extends beyond simple denial of service, as repeated exploitation could lead to persistent system instability and potentially create conditions for more sophisticated attacks.
Mitigation strategies for this vulnerability involve immediate firmware updates from Amazon to patch the kernel component, as the flaw exists in a specific version of the Fire OS kernel implementation. System administrators and device manufacturers should implement proper input validation mechanisms within kernel drivers to prevent similar issues from occurring in other implementations. The vulnerability highlights the importance of proper kernel security practices including bounds checking, argument validation, and memory management within device driver code. Additionally, implementing kernel security modules such as kernel address space layout randomization and stack canaries could provide additional protection against similar exploitation attempts, while monitoring for unauthorized device file access patterns can help detect potential exploitation attempts.