CVE-2021-41091 is a vulnerability affecting Moby, an open-source project created by Docker to enable software containerization. This bug originates from the data directory, typically located at `/var/lib/docker`, which contains subdirectories with insufficiently restricted permissions. As a result, unprivileged Linux users are able to traverse directory contents and execute programs that should be restricted.
The vulnerability has a CVSS score of 6.3, indicating a medium severity level. This is critical for organizations utilizing Docker, as it allows attackers with unprivileged access to execute programs in containers, potentially leading to unauthorized data access or modification.
Organizations should prioritize addressing this vulnerability by updating to Moby (Docker Engine) version 20.10.9 or higher. If an upgrade is not feasible, it is essential to limit access to the host and the host volumes to trusted users and containers only.
The urgency to patch this vulnerability is high as it can lead to significant security risks if exploited. Running containers should be stopped and restarted to ensure that the permissions are properly set after the update.
Vulnerability Details
This vulnerability allows unprivileged Linux users to execute programs within containers that have been granted extended permission bits (such as `setuid`). It becomes particularly problematic when the UID of an unprivileged user on the host matches the file owner or group inside a container, enabling those users to discover, read, and modify files.
The bug was identified and patched in Moby (Docker Engine) version 20.10.9. The effective remediation requires users to update as soon as possible, and for those unable to do so, to implement strict access controls.
Technical Analysis
The root cause of CVE-2021-41091 lies in the insufficient restriction of permissions on the data directory used by Docker containers. This oversight allows local users to navigate through the directory and execute programs, which can lead to privilege escalation if the user’s UID matches that of an executable file within a container.
The attack vector is categorized as local, with low complexity. This means that an attacker does not require advanced skills to exploit the vulnerability. The privileges required are low, and no user interaction is needed to trigger the vulnerability.
The impacts of this vulnerability are classified as low for confidentiality, integrity, and availability, indicating that while the risk is manageable, it is still significant enough to warrant immediate attention.
Risk & Impact Analysis
Risk to organizations includes unauthorized access to sensitive files and potential data breaches. The ease of exploitation due to low complexity means that organizations must act swiftly to mitigate this risk.
With a CVSS score of 6.3 and a high likelihood of successful exploitation, organizations should treat this vulnerability as a high priority in their patch management cycle.
The blast radius of this vulnerability could be significant, especially in environments where Docker is widely used for container orchestration and management. Therefore, organizations should prioritize patching immediately.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | Yes |
Public PoC | Yes |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The affected versions of Moby include all versions prior to 20.10.9. Additionally, Fedora versions 34 and 35 are also impacted. It is crucial for users to update their environments to the latest versions immediately.
Mitigation & Remediation
To mitigate this vulnerability, organizations should update to Moby (Docker Engine) version 20.10.9 or later as soon as possible. Running containers must be stopped and restarted to correct the permissions. For users unable to upgrade, it is advisable to limit access to the host and restrict volume access to trusted users and containers.
Continuous monitoring of systems for unauthorized access and behavior is essential to prevent exploitation of this vulnerability.
Detection Guidance
Organizations should monitor log indicators for any unauthorized access attempts related to Docker containers. Behavioral anomalies, such as unexpected execution of programs by unprivileged users, should be flagged. Additionally, network signatures related to Docker traffic may help in detecting exploitation attempts.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2021-41091 highlights the importance of strict permission management in containerized environments. Organizations should establish robust processes for evaluating and enforcing security controls within container orchestration tools.
This vulnerability represents a trend toward more sophisticated attacks against container environments, emphasizing the need for proactive vulnerability management. Security teams should prioritize education on privilege escalation and best practices for container security.
For further insights, organizations are encouraged to review best practices for establishing a solid security posture in containerized environments through penetration testing methodology.
Organizations can also benefit from engaging in designing a vulnerability management program to continuously assess and improve their security measures.
Finally, to ensure comprehensive security coverage, organizations should consider API security best practices as part of their overall strategy.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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