CVE-2016-6884 in MatrixSSL
Summary
by MITRE
TLS cipher suites with CBC mode in TLS 1.1 and 1.2 in MatrixSSL before 3.8.3 allow remote attackers to cause a denial of service (out-of-bounds read) via a crafted message.
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Analysis
by VulDB Data Team • 09/03/2020
The vulnerability identified as CVE-2016-6884 represents a critical security flaw in MatrixSSL versions prior to 3.8.3 that affects the handling of TLS cipher suites utilizing Cipher Block Chaining mode. This issue manifests as an out-of-bounds read condition that occurs during the processing of TLS messages, specifically when the protocol encounters cipher suites configured with CBC mode in TLS 1.1 and 1.2 implementations. The flaw exists within the cryptographic protocol stack where the software fails to properly validate input data structures before attempting to process them, creating a scenario where maliciously crafted TLS messages can trigger memory access violations.
The technical implementation of this vulnerability stems from insufficient input validation mechanisms within MatrixSSL's TLS processing routines. When the system receives a TLS message containing a cipher suite configured with CBC mode, the parsing logic does not adequately verify the boundaries of the incoming data before attempting to read from memory locations that may extend beyond the allocated buffer space. This particular weakness aligns with CWE-129, which categorizes improper validation of array indices, and specifically manifests as an out-of-bounds read condition that can be exploited through crafted TLS protocol messages. The vulnerability operates at the transport layer of the network stack, affecting the secure communication channel established between clients and servers using the affected SSL/TLS implementation.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it provides attackers with a mechanism to potentially disrupt service availability and could serve as a precursor to more sophisticated attacks. Remote attackers capable of sending specially crafted TLS messages can trigger the out-of-bounds read condition, causing the affected MatrixSSL implementation to crash or behave unpredictably, thereby leading to service disruption. This vulnerability particularly affects systems that rely on MatrixSSL for secure communications and could be exploited in distributed denial of service scenarios where multiple connections are established to overwhelm the target system. The ATT&CK framework categorizes this as a denial of service technique under the T1499 category, specifically targeting network services through protocol manipulation.
Mitigation strategies for CVE-2016-6884 require immediate deployment of MatrixSSL version 3.8.3 or later, which includes patches addressing the improper input validation in TLS cipher suite processing. Organizations should also implement network monitoring solutions to detect anomalous TLS traffic patterns that may indicate exploitation attempts, while disabling CBC-based cipher suites in TLS configurations where possible. The patch implementation addresses the root cause by introducing proper bounds checking and input validation mechanisms within the TLS message parsing routines, ensuring that all data structures are validated before memory access operations are performed. Security teams should also consider implementing intrusion detection systems that can identify and block malformed TLS messages attempting to exploit this vulnerability, while maintaining comprehensive logging of TLS connection attempts for forensic analysis purposes.