CVE-2026-30963

Description

Capsule is a multi-tenancy and policy-based framework for Kubernetes. To defend against namespace hijacking achieved through update/patch operations on namespaces, Capsule uses a webhook to validate update requests targeting namespaces. However, in Kubernetes, the namespace/finalize and namespace/status subresource APIs can also modify various fields of a namespace, including the metadata field. Prior to version 0.13.0, the webhook does not define interception rules for these subresources. As a result, if a tenant administrator has permission to modify namespace/status or namespace/finalize, they can successfully perform namespace hijacking. Version 0.13.0 fixes the issue. Another mitigation is to add two subresources (namespaces and snamespaces/status with namespace/finalize within it) to the resources list in the ValidatingWebhookConfiguration rules.

CVSS v3.1 Score

3.9

LOW

CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:L

EPSS — Exploit Prediction

0.0020

Probability of exploitation

0.10%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-20 Improper Input Validation

Affected Products

Vendor	Product	Versions
projectcapsule	capsule	< 0.13.0

References

Advisories & Patches

https://github.com/projectcapsule/capsule/security/advisories/GHSA-2ww6-hf35-mfjm https://github.com/projectcapsule/capsule/security/advisories/GHSA-2ww6-hf35-mfjm

Exploits

https://github.com/projectcapsule/capsule/security/advisories/GHSA-2ww6-hf35-mfjm https://github.com/projectcapsule/capsule/security/advisories/GHSA-2ww6-hf35-mfjm

Other References

https://github.com/projectcapsule/capsule/releases/tag/v0.13.0

Frequently Asked Questions

What is CVE-2026-30963? +

Capsule is a multi-tenancy and policy-based framework for Kubernetes. To defend against namespace hijacking achieved through update/patch operations on namespaces, Capsule uses a webhook to validate update requests targeting namespaces. However, in Kubernetes, the namespace/finalize and namespace/status subresource APIs can also modify various fields of a namespace, including the metadata field. Prior to version 0.13.0, the webhook does not define interception rules for these subresources. As a result, if a tenant administrator has permission to modify namespace/status or namespace/finalize, they can successfully perform namespace hijacking. Version 0.13.0 fixes the issue. Another mitigation is to add two subresources (namespaces and snamespaces/status with namespace/finalize within it) to the resources list in the ValidatingWebhookConfiguration rules. It has a CVSS v3.1 base score of 3.9 (LOW).

How severe is CVE-2026-30963? +

CVE-2026-30963 has a CVSS v3.1 score of 3.9 out of 10, rated LOW. This is a low-severity vulnerability with limited impact. The EPSS score is 0.0020, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-30963? +

CVE-2026-30963 affects products from projectcapsule, specifically: capsule. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-30963? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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