CVE-2021-22684 in RT RTOS
Summary
by MITRE • 08/31/2021
Tizen RT RTOS version 3.0.GBB is vulnerable to integer wrap-around in functions_calloc and mm_zalloc. This improper memory assignment can lead to arbitrary memory allocation, resulting in unexpected behavior such as a crash
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Analysis
by VulDB Data Team • 09/03/2021
The vulnerability identified as CVE-2021-22684 affects Tizen RT RTOS version 3.0.GBB and represents a critical integer wrap-around flaw in memory allocation functions. This issue manifests within the functions_calloc and mm_zalloc implementations where integer overflow conditions can occur during memory size calculations. The flaw stems from improper handling of arithmetic operations that should have been protected against overflow scenarios, creating a pathway for malicious actors to manipulate memory allocation parameters. The vulnerability falls under CWE-191, which specifically addresses integer underflow and overflow conditions, and aligns with ATT&CK technique T1059.001 for command and scripting interpreter usage in exploitation scenarios.
The technical implementation of this vulnerability involves the manipulation of integer variables during memory allocation requests where the system fails to validate that the calculated memory requirements remain within safe integer bounds. When the system processes allocation requests that exceed the maximum representable value for the integer type used in calculations, the wrap-around behavior causes the system to allocate memory at unexpected locations. This improper memory assignment can result in memory corruption, where adjacent memory regions become overwritten or accessed incorrectly, leading to system instability. The flaw particularly impacts the memory management subsystem where calloc and mm_zalloc functions are responsible for allocating and initializing memory blocks for application use.
The operational impact of this vulnerability extends beyond simple system crashes to encompass potential data corruption and unauthorized memory access patterns. When an attacker can trigger the integer wrap-around condition, they may be able to force the system to allocate memory at predetermined locations, potentially enabling code execution or privilege escalation attacks. The crash conditions that result from this vulnerability can be leveraged to perform denial of service attacks against embedded systems running Tizen RT, particularly those in IoT environments where system availability is critical. Systems utilizing this RTOS in automotive, industrial, or networking applications could face severe operational consequences if exploited.
Mitigation strategies for CVE-2021-22684 should focus on immediate code-level fixes within the memory allocation functions to prevent integer overflow conditions. The most effective approach involves implementing proper input validation and boundary checking before any arithmetic operations are performed on memory size parameters. Developers should ensure that all integer calculations in memory allocation routines include overflow detection mechanisms and that memory requests are validated against maximum allowable values. Additionally, implementing stack canaries and memory protection mechanisms can help detect and prevent exploitation attempts. Organizations should also consider upgrading to patched versions of Tizen RT if available, and conduct thorough security assessments of their embedded systems to identify potential exploitation vectors. The vulnerability highlights the importance of rigorous input validation in embedded systems and the critical need for proper integer handling in memory management functions to prevent similar issues in future implementations.