CVE-2021-3564 is a medium severity vulnerability in the Linux kernel, specifically related to double-free memory corruption within the HCI device initialization subsystem. This flaw allows a local user to attach a malicious HCI TTY Bluetooth device, leading to a potential crash of the system. The vulnerability affects all Linux kernel versions starting from 3.13, making it a widespread concern for organizations utilizing these systems.
The CVSS score of 5.5 indicates a medium level of risk, highlighting the need for organizations to remain vigilant. The attack vector is local with low complexity, meaning that exploitation requires low privileges and no user interaction, which increases the likelihood of successful attacks if unaddressed. The potential impact on availability is high, posing significant risks to systems that rely on the Linux kernel.
Organizations should prioritize patching immediately to mitigate this vulnerability, especially since its exploitation could lead to crashes and operational disruptions.
Given the critical nature of this vulnerability, it is essential for security teams to assess their environments, identify affected systems, and implement necessary updates to ensure resilience against this flaw.
Vulnerability Details
The vulnerability described in CVE-2021-3564 is a result of a flaw in the Linux kernel's HCI device initialization subsystem. Specifically, it involves a double-free memory corruption issue triggered when a local user attaches a malicious HCI TTY Bluetooth device. This vulnerability affects all Linux kernel versions starting from 3.13.
The CVSS score for this vulnerability is 5.5, categorized as medium severity. The attack vector is classified as local, requiring an attacker to have local access to exploit the vulnerability. The attack complexity is low, with the attacker requiring low privileges and no user interaction, which increases the risk of exploitation.
This vulnerability is classified under CWE-415, indicating an issue with double free operations. The potential impacts include high availability disruption, while confidentiality and integrity remain unaffected.
Technical Analysis
The root cause of CVE-2021-3564 lies in improper memory management within the Linux kernel's HCI device initialization subsystem. Specifically, the flaw occurs due to a double-free condition when a malicious HCI TTY Bluetooth device is attached by a local user. This flaw leads to the potential crash of the system.
The attack vector is classified as local, meaning that an attacker must have physical access or local user permissions to exploit the vulnerability. The attack complexity is low, allowing attackers with low privileges to trigger the issue without requiring any user interaction.
In terms of impact, the availability of affected systems is at high risk, as the vulnerability could lead to crashes and operational interruptions. However, there is no confidentiality or integrity impact associated with this vulnerability.
Risk & Impact Analysis
The real-world risk associated with CVE-2021-3564 primarily revolves around its potential to disrupt the availability of systems utilizing the affected Linux kernel versions. Given the local attack vector and low attack complexity, organizations must recognize that local users with malicious intent could leverage this vulnerability to crash systems.
This vulnerability is particularly concerning for environments that rely on continuous uptime and availability, such as servers and critical infrastructure. The blast radius could be extensive, affecting multiple systems if a malicious actor successfully exploits the vulnerability within a network.
Organizations should assess their current patching status and prioritize remediation efforts based on the potential impact of this vulnerability. The urgency should be categorized as high, given the medium severity score and the potential for significant operational disruptions.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
CVE-2021-3564 affects all Linux kernel versions starting from 3.13. Specific vulnerable configurations include:
- Debian Linux 9.0 and above - Fedora 34 and above - All versions of the Linux kernel from 3.13 onward.
Mitigation & Remediation
Organizations should prioritize patching immediately. To remediate the vulnerability, it is essential to upgrade to the latest patched version of the Linux kernel. For Debian users, consult the official Debian security advisory for the appropriate updates. Fedora users should check the Fedora security updates.
In instances where immediate patching is not feasible, consider implementing temporary workarounds, such as disabling Bluetooth functionalities until a patch is applied. Additionally, configuration hardening can help minimize the attack surface.
Organizations may also want to establish network controls to monitor and limit unauthorized access, as well as enhance logging and monitoring practices to detect potential exploitation attempts.
For further information on penetration testing services, organizations can explore penetration testing to validate the effectiveness of applied remediations.
Detection Guidance
Organizations should monitor logs for indicators of exploitation attempts, including unusual Bluetooth device connections or user actions indicative of unauthorized access. Behavioral anomalies such as unexpected crashes or system instability could also signal a potential exploitation of this vulnerability.
Furthermore, network signatures that detect abnormal traffic patterns associated with Bluetooth connections may help in identifying potential attacks. Regular system audits and monitoring changes to system configurations can serve as additional measures in detecting exploitation.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2021-3564 lies in the recurring issues associated with memory management flaws in kernel-level components. As vulnerabilities of this nature can lead to severe operational impacts, organizations should adopt proactive measures to assess their systems continuously.
This vulnerability represents a trend where local attack vectors are exploited with low complexity, emphasizing the need for robust security hygiene among local users. Security teams must prioritize educating users on the risks associated with local access and the importance of maintaining security best practices.
Strategically, this incident serves as a reminder that continuous vulnerability assessments and penetration testing are crucial in identifying potential weaknesses in systems. Organizations can enhance their resilience by investing in continuous security testing and adopting a proactive stance towards security.
To further understand the implications of vulnerabilities like CVE-2021-3564, organizations can benefit from comprehensive penetration testing methodologies and insights into best practices for vulnerability management.
By adopting these measures, organizations can better prepare themselves against potential exploitation and reduce the impact of vulnerabilities in their environments.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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