CVE-2019-1002101

The kubectl cp command allows copying files between containers and the user machine. To copy files from a container, Kubernetes creates a tar inside the container, copies it over the network, and kubectl unpacks it on the user’s machine. If the tar binary in the container is malicious, it could run any code and output unexpected, malicious results. An attacker could use this to write files to any path on the user’s machine when kubectl cp is called, limited only by the system permissions of the local user. The untar function can both create and follow symbolic links. The issue is resolved in kubectl v1.11.9, v1.12.7, v1.13.5, and v1.14.0.

Weakness

The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.

Affected Software

Potential Mitigations

• Follow the principle of least privilege when assigning access rights to entities in a software system.
• Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/132.html
• https://cwe.mitre.org/data/definitions/17.html
• https://cwe.mitre.org/data/definitions/35.html
• https://cwe.mitre.org/data/definitions/76.html

References

• http://www.openwall.com/lists/oss-security/2019/06/21/1
• http://www.openwall.com/lists/oss-security/2019/08/05/5
• http://www.securityfocus.com/bid/107652
• https://access.redhat.com/errata/RHBA-2019:0619
• https://access.redhat.com/errata/RHBA-2019:0620
• https://access.redhat.com/errata/RHBA-2019:0636
• https://access.redhat.com/security/cve/cve-2019-1002101
• https://github.com/kubernetes/kubernetes/pull/75037
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BPV2RE5RMOGUVP5WJMXKQJZUBBLAFZPZ/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QZB7E3DOZ5WDG46XAIU6K32CXHXPXB2F/
• https://www.twistlock.com/labs-blog/disclosing-directory-traversal-vulnerability-kubernetes-copy-cve-2019-1002101/