CVE-2016-6308 in OpenSSL
Summary
by MITRE
statem/statem_dtls.c in the DTLS implementation in OpenSSL 1.1.0 before 1.1.0a allocates memory before checking for an excessive length, which might allow remote attackers to cause a denial of service (memory consumption) via crafted DTLS messages.
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Analysis
by VulDB Data Team • 09/21/2022
The vulnerability identified as CVE-2016-6308 resides within the DTLS implementation of OpenSSL version 1.1.0 before 1.1.0a, specifically in the statem/statem_dtls.c file. This flaw represents a classic memory allocation issue that occurs during the processing of DTLS (Datagram Transport Layer Security) messages, where the system allocates memory resources before performing proper validation of message length parameters. The vulnerability stems from improper input validation procedures that fail to check for excessive message lengths prior to memory allocation, creating a scenario where malicious actors can exploit this weakness to consume excessive system resources.
The technical nature of this vulnerability aligns with CWE-129, which addresses improper validation of array index or buffer length, and specifically manifests as a memory consumption issue that can lead to denial of service conditions. When remote attackers craft specially designed DTLS messages with excessively long lengths, the OpenSSL implementation proceeds to allocate memory based on these crafted parameters without first verifying that the specified length falls within acceptable bounds. This premature allocation allows attackers to cause significant memory consumption on the target system, potentially leading to system instability or complete service unavailability.
From an operational perspective, this vulnerability presents a substantial risk to any system running OpenSSL 1.1.0 before 1.1.0a that handles DTLS traffic, particularly in environments where network services rely on secure datagram communication. The attack vector requires only the ability to send crafted DTLS messages to the target system, making it relatively easy to exploit in practice. The impact extends beyond simple resource exhaustion, as the vulnerability can affect the overall availability of network services that depend on DTLS functionality, potentially disrupting critical communication channels in web servers, VPN implementations, or other network infrastructure components that utilize OpenSSL's DTLS capabilities.
The mitigation strategy for CVE-2016-6308 primarily involves upgrading to OpenSSL version 1.1.0a or later, which includes the necessary patches to address the memory allocation timing issue. Additionally, implementing network-level protections such as rate limiting and connection monitoring can help detect and prevent exploitation attempts. Organizations should also consider deploying intrusion detection systems that can identify anomalous DTLS message patterns and establish proper input validation controls at network boundaries to reduce the attack surface. This vulnerability demonstrates the importance of proper resource management in cryptographic implementations and aligns with ATT&CK technique T1499.004, which covers network disruption through resource exhaustion attacks, highlighting the need for robust defensive measures in security-critical software components.