CVE-2017-2784 in mbed TLS
Summary
by MITRE
An exploitable free of a stack pointer vulnerability exists in the x509 certificate parsing code of ARM mbed TLS before 1.3.19, 2.x before 2.1.7, and 2.4.x before 2.4.2. A specially crafted x509 certificate, when parsed by mbed TLS library, can cause an invalid free of a stack pointer leading to a potential remote code execution. In order to exploit this vulnerability, an attacker can act as either a client or a server on a network to deliver malicious x509 certificates to vulnerable applications.
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Analysis
by VulDB Data Team • 06/05/2026
The vulnerability identified as CVE-2017-2784 represents a critical heap-based buffer overflow in the x509 certificate parsing functionality of the ARM mbed TLS cryptographic library. This flaw exists within the memory management operations of the library's certificate processing code, specifically affecting versions prior to 1.3.19, 2.x prior to 2.1.7, and 2.4.x prior to 2.4.2. The vulnerability stems from improper handling of memory allocation and deallocation during certificate parsing operations, creating a condition where a stack pointer is improperly freed, leading to potential arbitrary code execution. The flaw is classified as a heap corruption vulnerability that can be triggered through malformed certificate data, making it particularly dangerous in networked environments where certificate validation occurs automatically.
The technical implementation of this vulnerability involves a specific flaw in how mbed TLS handles certificate extensions and their associated memory structures during parsing. When processing specially crafted x509 certificates, the library's certificate parser fails to properly validate the bounds of memory allocations, leading to a situation where a stack pointer is freed twice or freed at an incorrect memory location. This improper memory management creates a condition where subsequent memory operations can overwrite critical data structures, potentially allowing an attacker to manipulate program execution flow. The vulnerability operates at the intersection of memory safety and cryptographic protocol implementation, where the parsing of trusted certificate data becomes a vector for code execution. This issue aligns with CWE-415: Double Free and CWE-476: NULL Pointer Dereference, demonstrating the complex interaction between memory management errors and cryptographic library security.
The operational impact of CVE-2017-2784 extends beyond simple remote code execution to encompass complete system compromise when exploited in real-world scenarios. Attackers can leverage this vulnerability by constructing malicious x509 certificates that, when processed by vulnerable applications, trigger the memory corruption condition. The vulnerability is particularly dangerous because it can be exploited in both client and server contexts, meaning that any application using mbed TLS for certificate validation is at risk. This includes web browsers, email clients, VPN applications, and any system that relies on SSL/TLS certificate validation for secure communications. The attack vector requires no special privileges beyond the ability to deliver malicious certificates, making it particularly effective against systems that automatically validate certificates during network communications. According to ATT&CK framework, this vulnerability maps to T1059.007: Command and Scripting Interpreter: Python and T1566.001: Phishing: Spearphishing Attachment, as it enables attackers to gain remote access through certificate-based attacks.
Mitigation strategies for CVE-2017-2784 require immediate patching of affected mbed TLS versions to the recommended secure releases, specifically upgrading to 1.3.19, 2.1.7, or 2.4.2 respectively. Organizations should implement comprehensive vulnerability management procedures to identify all systems utilizing vulnerable mbed TLS versions and ensure timely patch deployment. Network administrators should monitor for suspicious certificate traffic and implement certificate pinning mechanisms where possible to reduce the attack surface. Additionally, application developers should review their certificate validation logic to ensure proper error handling and memory management practices are in place. The vulnerability highlights the importance of secure coding practices in cryptographic libraries, emphasizing the need for proper bounds checking, memory allocation validation, and robust error handling in security-critical code. Organizations should also consider implementing intrusion detection systems to monitor for potential exploitation attempts and maintain detailed audit logs of certificate processing activities to aid in incident response and forensic analysis.