CVE-2021-22547 in IoT Devices SDK
Summary
by MITRE • 05/04/2021
In IoT Devices SDK, there is an implementation of calloc() that doesn't have a length check. An attacker could pass in memory objects larger than the buffer and wrap around to have a smaller buffer than required, allowing the attacker access to the other parts of the heap. We recommend upgrading the Google Cloud IoT Device SDK for Embedded C used to 1.0.3 or greater.
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Analysis
by VulDB Data Team • 05/07/2021
The vulnerability CVE-2021-22547 resides within the Google Cloud IoT Device SDK for Embedded C, specifically in the implementation of the calloc() memory allocation function. This flaw represents a classic buffer overflow condition that occurs when the SDK fails to validate the length parameter passed to the calloc() function. The absence of proper length validation creates a scenario where an attacker can manipulate memory allocation requests to exceed buffer boundaries, leading to heap corruption and potential memory access violations.
The technical implementation flaw stems from inadequate input validation within the memory management routines of the embedded SDK. When calloc() is invoked with an oversized parameter, the function does not perform proper bounds checking to ensure the requested memory allocation does not exceed available buffer limits. This oversight allows for integer overflow conditions where the memory allocation wraps around to a smaller value, effectively creating a situation where the allocated buffer is insufficient for the intended data structure. The vulnerability manifests as a heap-based buffer overflow that can be exploited to overwrite adjacent memory regions and potentially execute arbitrary code.
The operational impact of this vulnerability extends beyond simple memory corruption, as it provides attackers with opportunities to manipulate heap metadata and control program execution flow. Attackers can leverage this weakness to gain unauthorized access to other parts of the heap memory space, potentially leading to privilege escalation or information disclosure. The embedded nature of the IoT device SDK makes this particularly concerning as it operates in resource-constrained environments where memory management is critical for system stability and security. This vulnerability aligns with CWE-122, which describes heap-based buffer overflow conditions, and represents a significant risk in IoT deployments where devices may be remotely accessible and vulnerable to exploitation.
The recommended mitigation strategy involves upgrading to version 1.0.3 or greater of the Google Cloud IoT Device SDK for Embedded C, which includes proper length validation and bounds checking for memory allocation operations. Organizations should also implement additional security measures such as memory safety checks, heap integrity monitoring, and regular security assessments of their embedded IoT device implementations. This vulnerability demonstrates the critical importance of proper memory management in embedded systems and aligns with ATT&CK technique T1068, which covers local privilege escalation through memory corruption. The fix addresses the root cause by implementing comprehensive input validation that prevents maliciously crafted memory allocation requests from causing heap corruption and unauthorized memory access.