A newly identified security flaw, designated CVE-2024-7646, has been found in the popular ingress-nginx controller used in Kubernetes environments. This vulnerability presents a serious threat by allowing attackers to evade annotation validation processes, which can endanger Kubernetes clusters and requires urgent action from security professionals and cluster administrators.
The issue was uncovered by security researcher André Storfjord Kristiansen (@dev-bio on GitHub). It pertains to the way ingress-nginx handles annotations on Ingress objects. Annotations in Kubernetes serve as metadata that can influence the behavior of the ingress controller.
Exploiting this flaw enables attackers to insert harmful content into specific annotations, circumventing the usual validation procedures. This could potentially lead to arbitrary command execution and compromise the ingress-nginx controller’s credentials, which typically have extensive access to cluster secrets in standard setups.
Here’s a detailed look at the technical aspects of CVE-2024-7646 with example code:
Technical Overview of CVE-2024-7646
CVE-2024-7646 is a critical security issue affecting the ingress-nginx controller within Kubernetes. It enables attackers to bypass the validation of annotations. Here’s a breakdown of the technical details.
Research by Armosec reveals that the vulnerability resides in the validation process for annotations on Ingress objects. These annotations are used to attach metadata to Kubernetes objects and control various ingress behaviors.
The flaw allows attackers to insert malicious payloads, such as carriage return (\r) characters, into annotations. This bypasses the expected validation and can lead to arbitrary command execution.
Consider this example of a malicious Ingress object that exploits the vulnerability:
apiVersion: networking.k8s.io/v1 kind: Ingress metadata: name: malicious-ingress annotations: nginx.ingress.kubernetes.io/configuration-snippet: | more_set_headers “X-Malicious-Header: Benign”; more_set_headers “X-Hacked: True\r HTTP/1.1 200 OK Content-Type: text/html \r \r <html><body><h1>Hacked!</h1></body></html>
In this scenario, an attacker injects an HTTP response into the configuration-snippet annotation using carriage returns. When the ingress-nginx processes this annotation, it fails to properly validate or sanitize the input, resulting in the malicious response being sent to clients.
Exploiting CVE-2024-7646 could enable attackers to:
- Inject arbitrary HTTP responses, potentially facilitating Cross-Site Scripting (XSS) attacks.
- Execute arbitrary commands within the context of the ingress-nginx controller.
- Access the ingress-nginx controller’s credentials, which often have extensive permissions to cluster secrets.
This vulnerability is especially concerning in multi-tenant environments where non-administrative users can create Ingress objects.
