CVE-2021-3997 is a medium-severity vulnerability affecting Red Hat's Systemd, specifically related to uncontrolled recursion in systemd-tmpfiles. This flaw can lead to a denial of service at boot time when an excessive number of nested directories are created in the /tmp directory. The CVSS score for this vulnerability is 5.5, indicating a medium level of risk to organizations.
The potential impact of this vulnerability is significant. If an attacker or a misconfiguration results in the creation of many nested directories, it could prevent the system from booting properly, leading to downtime or service unavailability. As such, organizations running affected versions of Systemd should take immediate action to mitigate this risk.
Currently, there are no known exploits for this vulnerability reported in the wild, which means while it is essential to address the issue, the immediate threat level is lower compared to actively exploited vulnerabilities. Nevertheless, organizations should prioritize patching immediately.
This vulnerability impacts multiple versions of Red Hat's Systemd, Fedora, and Enterprise Linux, which underscores the need for vigilance in maintaining up-to-date systems and applying security patches promptly.
Vulnerability Details
The flaw in question allows for uncontrolled recursion within the systemd-tmpfiles component, particularly affecting systems where an excessive number of directories are created. The CVE was published on August 23, 2022, and has since been classified under CWE-674, indicating improper handling of recursion.
Affected systems include those running Systemd versions from 240 to versions prior to 250.2. Organizations utilizing Fedora versions 34 and 35, as well as various iterations of Red Hat Enterprise Linux (7.0, 8.0, and 9.0), are also vulnerable.
Technical Analysis
The root cause of CVE-2021-3997 lies in how systemd-tmpfiles processes directory structures. When too many nested directories are created, the system can enter a state of uncontrolled recursion, which results in a denial of service due to resource exhaustion.
This vulnerability primarily leverages local attack vectors, requiring low privileges to exploit. No user interaction is needed to initiate the denial of service condition, making it a considerable risk for systems that may inadvertently allow excessive directory nesting.
The availability impact is rated as high, indicating that the vulnerability can lead to significant disruption of services. However, confidentiality and integrity impacts are not applicable in this scenario.
Risk & Impact Analysis
Organizations utilizing affected versions of Red Hat's Systemd must recognize the potential for operational disruption. The ability to induce a denial of service at boot time through a simple recursive directory creation is a significant risk, especially for production environments.
Given the classification of this vulnerability, organizations should assess their exposure and prioritize remediation. With a CVSS score of 5.5, the urgency is moderate; however, the potential for downtime escalates the need for prompt action.
Implementing proper directory management and monitoring can help mitigate the risk associated with this vulnerability. Additionally, organizations should stay informed about updates and advisories that pertain to their systems.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
This vulnerability affects all versions of Systemd from 240 up to but not including 250.2. Additionally, the vulnerability is present in Fedora versions 34 and 35, as well as Red Hat Enterprise Linux versions 7.0, 8.0, and 9.0.
Mitigation & Remediation
Organizations should apply the latest security patches for Systemd as they become available. For those unable to immediately upgrade, implementing strict directory creation policies and monitoring /tmp directory activities can serve as a workaround.
For detailed guidance on security practices, consider reviewing the penetration testing methodologies that can help identify similar weaknesses.
Detection Guidance
To detect potential exploitation of this vulnerability, organizations should monitor log files for unusual directory creation patterns and file system changes, particularly in the /tmp directory. Behavioral anomalies related to system boot processes should also be flagged for review.
AppSecure Threat Intelligence Insight
The significance of CVE-2021-3997 lies in its representation of potential pitfalls in systems management, particularly in how directory structures are handled. Security teams should take this as a reminder of the importance of rigorous testing and adherence to security principles during software development.
Additionally, this vulnerability highlights the need for ongoing education regarding secure coding practices and system configuration management. By leveraging resources such as the vulnerability management program, organizations can better prepare for and mitigate similar vulnerabilities in the future.
Overall, this vulnerability serves as a critical learning opportunity for security teams, emphasizing the need for continuous vigilance and improvement in security posture.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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