CVE-2021-39251 is a high-severity vulnerability affecting the NTFS-3G file system driver. This vulnerability allows a crafted NTFS image to cause a NULL pointer dereference in the function ntfs_extent_inode_open, leading to potential system instability or crash. The CVSS score for this vulnerability is 7.8, indicating a high level of risk. Organizations should prioritize patching immediately to avoid potential impact.
The vulnerability was published on September 7, 2021, and affects NTFS-3G versions prior to 2021.8.22. It is essential for users of Debian, Red Hat, and Fedora operating systems to be aware of this issue as it poses significant risks to their environments.
Given that this vulnerability has a local attack vector and requires low privileges, it is particularly concerning for environments where untrusted users may have access. The potential impacts include severe degradation of system performance and loss of data integrity.
Currently, there are no known exploits available for this vulnerability, but organizations are urged to take proactive measures to mitigate any potential risk.
Vulnerability Details
The official description of CVE-2021-39251 states that a crafted NTFS image can cause a NULL pointer dereference in ntfs_extent_inode_open in NTFS-3G versions earlier than 2021.8.22. This vulnerability is classified under CWE-476 (NULL Pointer Dereference) and CWE-20 (Improper Input Validation).
The CVSS version 3.1 score of 7.8 indicates high severity, reflecting the potential impact on confidentiality, integrity, and availability. The attack vector is local, meaning it requires physical or local access to the system, and the attack complexity is low, as the attacker does not need to perform significant effort to exploit the vulnerability.
Affected products include NTFS-3G, Debian Linux versions 9.0, 10.0, and 11.0, as well as Red Hat Enterprise Linux versions 7.0 and 8.0. The vulnerability was disclosed on September 7, 2021.
Technical Analysis
The root cause of this vulnerability lies in the handling of NTFS images by the NTFS-3G file system driver. Specifically, the vulnerability stems from insufficient validation of input data, which can lead to dereferencing a NULL pointer in the ntfs_extent_inode_open function.
The attack vector is classified as local, meaning an attacker must have access to the system where the NTFS-3G driver is used. The attack complexity is low, as no specialized knowledge or significant effort is required to exploit the vulnerability. Privileges required are low, which can allow even non-administrative users to exploit the issue.
User interaction is not required for exploitation, and the confidentiality, integrity, and availability impacts are all rated as high, indicating a severe risk to affected systems.
Risk & Impact Analysis
Risk to organizations includes potential system instability, data loss, and unauthorized access to sensitive information. The high severity rating and the potential impact on confidentiality, integrity, and availability should prompt organizations to take immediate action.
Given that this vulnerability can be exploited locally, it poses a significant risk, especially in multi-user environments. The blast radius could extend to all users with local access, making it critical for organizations to address this vulnerability in their patch management cycle.
Organizations should prioritize patching immediately, as the vulnerability has been marked as modified and remains unexploited in the wild. The urgency for remediation is high, given the potential impact on systems using affected versions.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
Affected versions include NTFS-3G versions prior to 2021.8.22, as well as Debian Linux versions 9.0, 10.0, and 11.0. Additionally, Red Hat Enterprise Linux versions 7.0 and 8.0, including its advanced virtualization component, and Fedora versions 33 and 35 are also impacted.
Mitigation & Remediation
To remediate this vulnerability, organizations should upgrade to NTFS-3G version 2021.8.22 or later. If a patch is not immediately available, consider implementing configuration hardening and network controls to limit access to systems that utilize the vulnerable NTFS-3G version.
Organizations can also benefit from conducting regular penetration testing to identify any vulnerabilities in their systems. For more information on effective penetration testing practices, refer to our guide on penetration testing that exercises the patched code path.
Detection Guidance
Monitor logs for unusual activity related to NTFS-3G, particularly when users attempt to access NTFS images. Look for any behavioral anomalies that could indicate exploitation attempts, such as unexpected system crashes or performance degradation.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2021-39251 lies in the potential for similar vulnerabilities to be discovered in other file handling systems. Security teams should analyze the patterns that led to this vulnerability and implement preventative measures to avoid similar issues in the future.
Organizations are encouraged to develop a robust vulnerability management program to ensure timely patching and assessment of their systems. For best practices in vulnerability management, refer to our blog on vulnerability management programs that can help reduce the attack surface.
Additionally, security teams should conduct regular assessments to identify and mitigate risks associated with file handling vulnerabilities. For more insights on proactive measures, check our article on penetration testing methodology to stay ahead of potential threats.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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