A security issue was discovered in Kubernetes where a user may be able to create a container with subpath volume mounts to access files & directories outside of the volume, including on the host filesystem. This vulnerability has a CVSS score of 8.8, indicating a high severity level. Organizations using vulnerable versions of Kubernetes should be aware of the potential risks this vulnerability exposes.
Risk to organizations includes unauthorized access to sensitive information stored on the host filesystem, which could lead to data breaches or further exploitation of the system. Given the nature of this vulnerability, it is crucial for organizations to assess their exposure and implement remediation strategies.
Currently, this vulnerability does not appear to have a known exploit publicly available, but its potential for exploitation remains high. Organizations should prioritize patching immediately to mitigate risks associated with this vulnerability.
The urgency for defenders is underscored by the high CVSS score and the potential impact of the vulnerability on the security of Kubernetes environments.
Vulnerability Details
The vulnerability identified as CVE-2021-25741 affects Kubernetes, specifically allowing users to create containers with subpath volume mounts that can access files and directories outside of the intended volume. The official CVE description notes that this could include access to the host filesystem, thereby resulting in serious security implications.
The CVSS v3.1 score for this vulnerability is 8.8, categorized as high severity. This score reflects the network attack vector (AV:N), low attack complexity (AC:L), and low privileges required (PR:L) for exploitation. The confidentiality, integrity, and availability impacts are all high (C:H, I:H, A:H), highlighting the critical nature of this issue.
The publication date of this vulnerability was September 20, 2021, and it has since been modified. The vulnerability is classified under CWE-20 and CWE-552, indicating potential issues with improper input validation and file access control.
Technical Analysis
The root cause of CVE-2021-25741 lies in the way Kubernetes handles subpath volume mounts. Attackers may leverage this flaw to create containers that gain access to unauthorized files outside the designated volume, including critical files on the host machine. The attack vector is through the network, requiring low complexity and low privileges for execution.
This vulnerability requires no user interaction, which increases the risk of exploitation. The impacts on confidentiality and integrity are significant, as unauthorized access to sensitive data and manipulation of files can occur. Availability impact is also highlighted, as it could lead to disruptions in service.
Risk & Impact Analysis
Organizations using affected versions of Kubernetes are at significant risk. The ability to access host filesystem files can lead to data breaches, loss of sensitive information, and potential further exploitation of the environment. This vulnerability has a broad blast radius, affecting all installations of Kubernetes that meet the version criteria.
Given the CVSS score of 8.8 and the implications of this vulnerability, organizations should address this issue in their priority patch cycle. The potential for exploitation underscores the need for immediate action in ensuring the security of Kubernetes environments.
Signal | Status |
|---|---|
Known Exploit | Yes |
Public PoC | Yes |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
This vulnerability affects Kubernetes versions up to 1.19.14, as well as versions from 1.20.0 to 1.20.10, 1.21.0 to 1.21.4, and 1.22.0 to 1.22.1. Organizations should verify their Kubernetes installations against these version ranges and take necessary actions.
Mitigation & Remediation
To mitigate this vulnerability, organizations should upgrade to the latest version of Kubernetes that addresses this issue. If a patch is not yet available, consider applying configuration hardening measures to limit access controls and monitor for suspicious activity. Implementing network controls can also help prevent unauthorized access.
For more information on how to secure your Kubernetes environment, organizations can refer to our penetration testing services.
Detection Guidance
Organizations should monitor logs for any indicators of unauthorized file access, unusual volume mount activity, or unexpected container behavior. Behavioral anomalies should be logged and investigated. Implementing network signatures that alert on suspicious container activities can also help in early detection.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2021-25741 reveals a pattern of vulnerabilities that can arise from misconfigurations in container orchestration systems like Kubernetes. As organizations increasingly adopt cloud-native architectures, understanding the risks associated with container security becomes paramount.
This vulnerability highlights the need for security teams to integrate security practices into the development lifecycle and continuously monitor their environments for emerging threats. For further guidance on best practices, organizations can refer to our penetration testing methodology and the vulnerability management program design.
Security teams should also consider the importance of proactive assessments and engage in regular security testing of their environments to identify and address vulnerabilities before they can be exploited.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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