CVE-2020-24585 in wolfSSL
Summary
by MITRE
An issue was discovered in the DTLS handshake implementation in wolfSSL before 4.5.0. Clear DTLS application_data messages in epoch 0 do not produce an out-of-order error. Instead, these messages are returned to the application.
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Analysis
by VulDB Data Team • 08/22/2020
The vulnerability identified as CVE-2020-24585 resides within the DTLS handshake implementation of wolfSSL cryptographic library versions prior to 4.5.0. This flaw specifically affects the handling of application data messages during the initial handshake phase, where messages are transmitted in epoch 0. The issue represents a significant security weakness in the protocol's message processing logic, as it fails to properly validate the timing and ordering of DTLS application data. The DTLS protocol is designed to provide secure communication over unreliable transport protocols like UDP, and its handshake mechanism must maintain strict ordering and timing constraints to ensure security properties are preserved.
The technical flaw manifests when clear DTLS application_data messages are received in epoch 0, which is the initial epoch during the DTLS handshake process. In a properly functioning implementation, messages arriving in epoch 0 should be rejected or handled according to specific protocol rules that prevent unauthorized data transmission before the handshake completes. However, the vulnerable wolfSSL implementation allows these early epoch messages to be passed directly to the application layer without proper validation. This behavior creates a potential attack vector where malicious actors could inject application data before the secure channel is properly established, undermining the fundamental security assumptions of the DTLS protocol.
From an operational impact perspective, this vulnerability compromises the integrity and confidentiality guarantees that DTLS is designed to provide. Attackers could potentially exploit this flaw to inject malicious application data into the communication stream before the secure session is properly negotiated. The implications extend beyond simple data injection, as this weakness could enable more sophisticated attacks such as man-in-the-middle interference or session hijacking attempts. The vulnerability affects any system using wolfSSL versions before 4.5.0 that relies on DTLS for secure communication, particularly in IoT devices, embedded systems, and applications where DTLS is used for secure data transmission over UDP networks.
This vulnerability maps to CWE-310 in the Common Weakness Enumeration, specifically relating to cryptographic issues in the implementation of secure protocols. The flaw demonstrates poor input validation and improper state handling during protocol negotiation, which aligns with ATT&CK technique T1071.004 for application layer protocol manipulation. Organizations implementing DTLS-based security solutions should prioritize upgrading to wolfSSL version 4.5.0 or later, as this release includes proper validation of epoch timing for application data messages. Additional mitigations include implementing network-level filtering to prevent unauthorized DTLS traffic, monitoring for unusual epoch transitions, and conducting thorough security audits of all DTLS implementations within the infrastructure. The fix addresses the root cause by ensuring that application data messages in epoch 0 are properly rejected or handled according to DTLS specification requirements, thereby restoring the intended security properties of the protocol.