CVE-2019-20786 in DTLS
Summary
by MITRE
handleIncomingPacket in conn.go in Pion DTLS before 1.5.2 lacks a check for application data with epoch 0, which allows remote attackers to inject arbitrary unencrypted data after handshake completion.
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Analysis
by VulDB Data Team • 06/01/2024
The vulnerability identified as CVE-2019-20786 resides within the Pion DTLS implementation, specifically in the handleIncomingPacket function located in conn.go. This flaw represents a critical security weakness in the Datagram Transport Layer Security protocol implementation that affects versions prior to 1.5.2. The vulnerability stems from an insufficient validation mechanism that fails to properly verify the epoch value of application data packets received after the handshake completion phase.
The technical flaw manifests as the absence of epoch validation for application data packets during the DTLS connection lifecycle. In DTLS protocols, epochs represent distinct cryptographic states that define when certain security parameters become active. When the handshake completes, application data should be processed within the established cryptographic context, typically with epochs greater than zero. However, the vulnerable implementation fails to reject application data packets that arrive with epoch 0, which should only be valid during the initial handshake phase.
This vulnerability allows remote attackers to inject arbitrary unencrypted data into the DTLS connection after the handshake has been completed. The impact extends beyond simple data injection as it fundamentally undermines the cryptographic integrity of the connection. Attackers can exploit this weakness to inject plaintext data that bypasses normal encryption mechanisms, potentially leading to data corruption, information disclosure, or even privilege escalation depending on the application context. The flaw operates at the protocol level, making it particularly dangerous as it affects the core security guarantees provided by DTLS.
From an operational perspective, this vulnerability creates a window of opportunity for attackers to manipulate data flows within DTLS connections. The attack requires the adversary to be in a position to intercept and modify network traffic between the DTLS endpoints, but once successful, it can compromise the confidentiality and integrity of communications. The vulnerability is particularly concerning because it affects the fundamental security assumptions of DTLS implementations, potentially allowing attackers to inject malicious payloads that appear legitimate to the receiving application.
The weakness aligns with CWE-310, which addresses cryptographic issues related to insufficient validation of cryptographic parameters, and relates to ATT&CK technique T1071.004 for application layer protocol usage. Organizations utilizing Pion DTLS implementations should prioritize immediate patching to version 1.5.2 or later, which includes proper epoch validation checks. Additional mitigations may include network-level monitoring for unusual packet patterns, implementing strict connection validation procedures, and ensuring that all DTLS endpoints are updated to versions that properly enforce epoch boundaries. Security teams should also consider implementing intrusion detection systems that can identify potential exploitation attempts targeting this specific vulnerability pattern.