Improper path handling in Kustomization files allows for denial of service

Description

The kustomize-controller enables the use of Kustomize’s functionality when applying Kubernetes declarative state onto a cluster. A malicious user can use a specially crafted kustomization.yaml to cause Denial of Service at controller level.

In multi-tenancy deployments this can lead to multiple tenants not being able to apply their Kustomizations until the malicious kustomization.yaml is removed and the controller restarted.

Impact

Within the affected versions, users with write access to a Flux source are able to craft a malicious kustomization.yaml file which causes the controller to enter an endless loop.

Patches

This vulnerability was fixed in kustomize-controller v0.24.0 and included in flux2 v0.29.0 released on 2022-04-20. The changes introduce better handling of Kustomization files blocking references that could lead to endless loops.

Credits

The Flux engineering team found and patched this vulnerability.

For more information

If you have any questions or comments about this advisory please open an issue in the flux2 repository.

Basic information

Type
reviewed
Severity
high
Advisory on GitHub
Open advisory ↗
Repository advisory
Open repository advisory ↗
Source code
Browse source ↗
Published (advisory)
2022-05-20 16:58:38 UTC
Updated
2023-01-27 05:01:57 UTC
GitHub reviewed
2022-05-20 16:58:38 UTC
NVD published
2022-05-05

EPSS Score

Score Percentile
0.31% 53.71%

CVSS Scores

Base score Version Severity Vector
7.7 3.1
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.

Identifiers

CWEs

CWE id Name
CWE-674 Uncontrolled Recursion

Credits

  • hiddeco (analyst)

Affected packages (2)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
go github.com/fluxcd/kustomize-controller >= 0.16.0, < 0.24.0 0.24.0
go github.com/fluxcd/flux2 >= 0.19.0, < 0.29.0 0.29.0

References

cvelogic Threat Intelligence