CVE-2021-22156 in QNX Software Development Platform
Summary
by MITRE • 08/17/2021
An integer overflow vulnerability in the calloc() function of the C runtime library of affected versions of BlackBerry® QNX Software Development Platform (SDP) version(s) 6.5.0SP1 and earlier, QNX OS for Medical 1.1 and earlier, and QNX OS for Safety 1.0.1 and earlier that could allow an attacker to potentially perform a denial of service or execute arbitrary code.
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Analysis
by VulDB Data Team • 08/22/2025
The integer overflow vulnerability identified as CVE-2021-22156 resides within the calloc() function of the C runtime library in several BlackBerry QNX operating system variants. This flaw affects QNX Software Development Platform versions 6.5.0SP1 and earlier, QNX OS for Medical 1.1 and earlier, and QNX OS for Safety 1.0.1 and earlier. The vulnerability stems from improper handling of integer arithmetic during memory allocation operations, creating a condition where an attacker can manipulate input parameters to cause unexpected behavior in the memory management system. The calloc() function is designed to allocate memory and initialize it to zero, but when integer overflow occurs during parameter validation, the function may not allocate the expected amount of memory or may allocate memory at incorrect offsets within the address space. This vulnerability represents a critical weakness in the system's memory management subsystem and aligns with CWE-190, Integer Overflow or Wraparound, which specifically addresses issues where integer arithmetic produces results that exceed the maximum value representable by the data type. The flaw exists at the foundational level of the operating system's runtime environment, making it particularly dangerous as it can be exploited across various QNX-based systems including those in medical and safety-critical applications.
The technical exploitation of this vulnerability occurs when an attacker provides malicious input to the calloc() function that causes integer overflow during the calculation of memory requirements. When the function attempts to compute the total memory needed for allocation, an integer overflow condition results in a smaller value being used for allocation than originally intended. This can lead to several potential outcomes including memory corruption, heap corruption, or allocation of insufficient memory which may trigger a segmentation fault or other system instability. The vulnerability is particularly concerning because calloc() is a commonly used memory allocation function throughout system applications and embedded software, meaning that exploitation could affect a wide range of system components. The integer overflow specifically manifests when the product of the number of elements and element size exceeds the maximum value that can be represented by the integer type used for the calculation, causing the result to wrap around to a small positive value or zero. This behavior creates a pathway for attackers to potentially manipulate the memory allocation process to achieve unauthorized memory access patterns that could lead to privilege escalation or code execution.
The operational impact of CVE-2021-22156 extends beyond simple denial of service scenarios to potentially enable arbitrary code execution in affected systems. In environments where QNX operates as a core component of embedded systems, such as medical devices or automotive safety systems, this vulnerability could be leveraged to compromise system integrity and potentially endanger human safety. The vulnerability's exploitation could result in system crashes, data corruption, or unauthorized access to sensitive system resources, making it particularly dangerous in safety-critical applications where system reliability is paramount. Systems running affected QNX versions may experience unpredictable behavior when processing memory allocation requests that trigger the integer overflow condition, leading to potential system instability or complete system failure. The vulnerability's impact is amplified by the fact that many embedded applications rely heavily on the calloc() function for memory management, meaning that a single exploitation attempt could potentially affect multiple system components. Organizations using these operating system versions face significant risk of operational disruption, particularly in environments where continuous system availability is critical.
Mitigation strategies for CVE-2021-22156 should prioritize immediate patching of affected QNX operating system versions through official BlackBerry QNX security updates. System administrators should implement comprehensive monitoring of memory allocation patterns and anomalous system behavior that could indicate exploitation attempts. The vulnerability's nature suggests that input validation and bounds checking should be enhanced at all levels where calloc() or similar memory allocation functions are used, implementing additional safeguards to prevent integer overflow conditions. Organizations should also consider implementing runtime protection mechanisms such as stack canaries, address space layout randomization, and heap integrity checks to detect and prevent exploitation attempts. The mitigation approach should align with ATT&CK technique T1059.007 for Command and Scripting Interpreter and T1499.004 for Endpoint Denial of Service, as attackers may attempt to leverage this vulnerability for system disruption or code execution. Additionally, defensive measures should include regular security assessments of embedded systems and implementation of secure coding practices that prevent integer overflow conditions in memory management functions. Network segmentation and access controls should be reinforced to limit potential attack vectors, particularly in medical and safety-critical environments where the vulnerability could have severe consequences.