CVE-2021-3655 in Linux
Summary
by MITRE • 08/06/2021
A vulnerability was found in the Linux kernel in versions before v5.14-rc1. Missing size validations on inbound SCTP packets may allow the kernel to read uninitialized memory.
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Analysis
by VulDB Data Team • 08/08/2021
The vulnerability identified as CVE-2021-3655 represents a critical memory safety issue within the Linux kernel's SCTP (Stream Control Transmission Protocol) implementation. This flaw exists in kernel versions prior to v5.14-rc1 and specifically targets the handling of inbound SCTP packets where proper size validation mechanisms are absent. The vulnerability stems from inadequate input sanitization during packet processing, creating a pathway for potential memory disclosure attacks that could expose sensitive data residing in kernel memory spaces.
This technical flaw falls under the category of uninitialized memory access, which is classified as CWE-128 in the Common Weakness Enumeration taxonomy. The vulnerability occurs when the SCTP implementation fails to validate the size of incoming packets before processing them, allowing malicious actors to craft specially crafted packets that trigger the kernel to read memory regions that have not been properly initialized. The absence of size checks creates an opportunity for attackers to potentially extract kernel memory contents, including sensitive information such as cryptographic keys, passwords, or other confidential data that may be stored in memory.
The operational impact of this vulnerability extends beyond simple memory disclosure, as it provides attackers with a potential foothold for more sophisticated attacks within the kernel space. According to ATT&CK framework, this vulnerability could be leveraged as part of a broader attack chain under the technique T1059.001 for command execution and T1068 for exploit development. The vulnerability affects systems running Linux kernel versions below 5.14-rc1, making it particularly concerning for organizations that have not yet upgraded their kernel versions. The implications are significant for network services that rely on SCTP, as the protocol is commonly used in telecommunications signaling, financial services, and other critical infrastructure applications where memory integrity is paramount.
Mitigation strategies for CVE-2021-3655 primarily focus on kernel version upgrades to v5.14-rc1 or later, which contain the necessary patches to address the missing size validation checks. System administrators should prioritize upgrading production environments to ensure protection against this vulnerability. Additionally, network-level mitigations such as implementing firewall rules to restrict SCTP traffic or deploying intrusion detection systems that can identify suspicious packet patterns may provide temporary protection. The vulnerability highlights the importance of proper input validation and memory safety practices in kernel development, emphasizing that even seemingly minor oversights in protocol implementation can result in significant security implications. Organizations should conduct thorough vulnerability assessments to identify systems running affected kernel versions and implement comprehensive patch management procedures to maintain system integrity.