CVE-2023-30840

Fluid is an open source Kubernetes-native distributed dataset orchestrator and accelerator for data-intensive applications. Starting in version 0.7.0 and prior to version 0.8.6, if a malicious user gains control of a Kubernetes node running fluid csi pod (controlled by the csi-nodeplugin-fluid node-daemonset), they can leverage the fluid-csi service account to modify specs of all the nodes in the cluster. However, since this service account lacks list node permissions, the attacker may need to use other techniques to identify vulnerable nodes.

Once the attacker identifies and modifies the node specs, they can manipulate system-level-privileged components to access all secrets in the cluster or execute pods on other nodes. This allows them to elevate privileges beyond the compromised node and potentially gain full privileged access to the whole cluster.

To exploit this vulnerability, the attacker can make all other nodes unschedulable (for example, patch node with taints) and wait for system-critical components with high privilege to appear on the compromised node. However, this attack requires two prerequisites: a compromised node and identifying all vulnerable nodes through other means.

Version 0.8.6 contains a patch for this issue. As a workaround, delete the csi-nodeplugin-fluid daemonset in fluid-system namespace and avoid using CSI mode to mount FUSE file systems. Alternatively, using sidecar mode to mount FUSE file systems is recommended.

Weakness

The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions.

Affected Software

Extended Description

Assuming a user with a given identity, authorization is the process of determining whether that user can access a given resource, based on the user’s privileges and any permissions or other access-control specifications that apply to the resource. When access control checks are incorrectly applied, users are able to access data or perform actions that they should not be allowed to perform. This can lead to a wide range of problems, including information exposures, denial of service, and arbitrary code execution.

Potential Mitigations

• Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) [REF-229] to enforce the roles at the appropriate boundaries.
• Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
• For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
• For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page.
• One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.

References

• https://github.com/fluid-cloudnative/fluid/commit/77c8110a3d1ec077ae2bce6bd88d296505db1550
• https://github.com/fluid-cloudnative/fluid/commit/91c05c32db131997b5ca065e869c9918a125c149
• https://github.com/fluid-cloudnative/fluid/releases/tag/v0.8.6
• https://github.com/fluid-cloudnative/fluid/security/advisories/GHSA-93xx-cvmc-9w3v
• https://github.com/fluid-cloudnative/fluid/commit/77c8110a3d1ec077ae2bce6bd88d296505db1550
• https://github.com/fluid-cloudnative/fluid/commit/91c05c32db131997b5ca065e869c9918a125c149
• https://github.com/fluid-cloudnative/fluid/releases/tag/v0.8.6
• https://github.com/fluid-cloudnative/fluid/security/advisories/GHSA-93xx-cvmc-9w3v