CVE-2021-43301 in PJSIP
Summary
by MITRE • 02/17/2022
Stack overflow in PJSUA API when calling pjsua_playlist_create. An attacker-controlled 'file_names' argument may cause a buffer overflow since it is copied to a fixed-size stack buffer without any size validation.
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Analysis
by VulDB Data Team • 11/05/2025
The vulnerability identified as CVE-2021-43301 represents a critical stack buffer overflow flaw within the PJSUA API, specifically when invoking the pjsua_playlist_create function. This issue stems from inadequate input validation mechanisms that fail to properly constrain the size of attacker-controlled data being processed. The vulnerability manifests when the file_names argument, which is intended to specify playlist file paths, is copied directly into a fixed-size stack buffer without any bounds checking or size validation measures. This fundamental design flaw creates an exploitable condition where malicious input can exceed the allocated buffer space, leading to potential memory corruption and arbitrary code execution. The vulnerability directly maps to CWE-121 Stack-based Buffer Overflow, which is classified under the broader category of buffer overflow weaknesses that occur when data is written beyond the bounds of a stack-allocated buffer. From an operational perspective, this vulnerability poses significant risks to systems utilizing the PJSUA API for multimedia communication services, particularly in environments where playlist creation functionality is exposed to untrusted input sources. The attack surface expands when considering that the PJSUA API is commonly used in VoIP applications, multimedia frameworks, and communication platforms where playlist management is a standard feature. An attacker could leverage this vulnerability to execute arbitrary code on the target system with the privileges of the affected application, potentially leading to complete system compromise. The exploitation requires careful crafting of the file_names argument to overflow the stack buffer, which can be achieved through specifically constructed input strings that exceed the predetermined buffer limits. This type of vulnerability aligns with ATT&CK technique T1059.007 Command and Scripting Interpreter: PowerShell, as attackers may utilize PowerShell or similar scripting capabilities to generate malicious input payloads that trigger the buffer overflow condition. The impact extends beyond immediate code execution to include potential denial of service conditions, data corruption, and information disclosure. Organizations using applications built on the PJSUA API should prioritize immediate mitigation through input validation patches, stack buffer size restrictions, and application sandboxing measures. The vulnerability demonstrates the critical importance of implementing proper input validation and bounds checking in API implementations, particularly for functions that process external data. Security practitioners should implement defensive programming practices including stack canaries, address space layout randomization, and heap-based buffer overflow protections as additional layers of defense. The vulnerability also highlights the necessity of regular security code reviews and static analysis tools to identify similar buffer overflow patterns in legacy codebases. Mitigation strategies should include immediate patching of affected software versions, implementation of strict input validation for all external data sources, and deployment of intrusion detection systems to monitor for exploitation attempts. Additionally, application developers should consider migrating to safer programming practices and modern memory-safe languages or implementing comprehensive buffer overflow protection mechanisms to prevent similar vulnerabilities from emerging in future releases.