# Crossplane Runtime signature verification TOCTOU race condition

Source: https://junglewise.ai/threats/go-2026-6302-signature-verification-toctou-allows-installing-unverified-4e39ceaa  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-09. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

Severity: info · Published 2026-09-09

Crossplane Runtime's package manager can be tricked into installing unsigned packages through a time-of-check-time-of-use (TOCTOU) race condition in signature verification. When pulling packages by tag reference from untrusted registries, an attacker can serve a correctly signed image for verification, then swap it with an unsigned malicious image during installation. This allows installation of unverified packages that could contain malicious code.

Technologies: [Crossplane Runtime](https://junglewise.ai/threats/technologies/crossplane-runtime). Vendors: [Crossplane](https://junglewise.ai/threats/vendors/crossplane), [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Informational severity, published 9 September 2026.

**Which products and versions are affected?** Crossplane Runtime 2.3.0 to 2.3.2, 2.4.0-rc.0 to 2.4.0-rc.0; github.com/crossplane/crossplane-runtime/v2 (Go) SEMVER:introduced=2.3.0,fixed=2.3.3,introduced=2.4.0-rc.0,fixed=2.4.0-rc.1.

**Is there a fix for This vulnerability?** Yes. github.com/crossplane/crossplane-runtime/v2 (Go): upgrade to 2.4.0-rc.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked over the network, in a software library.

**Am I affected?** Check whether you run Crossplane Runtime or github.com/crossplane/crossplane-runtime/v2 (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/crossplane/crossplane-runtime/v2 (Go): upgrade to 2.4.0-rc.1 or later

  ```sh
  go get github.com/crossplane/crossplane-runtime/v2@v2.4.0-rc.1
  ```


## Technical details

The vulnerability exists in the xpkg package manager's CachedClient.Get function, which resolves OCI tag references separately for signature verification and image fetching. An attacker controlling a registry can perform a race condition attack, serving a signed image during verification and an unsigned image during fetch. The fix resolves tag references once and uses the resulting digest for both operations. The vulnerability requires three preconditions: signature verification configured, tag-based (not digest-based) installation, and use of untrusted registries.

## Affected products

- Crossplane Runtime 2.3.0 to 2.3.2, 2.4.0-rc.0 to 2.4.0-rc.0

## Timeline

- 2026-06-15: disclosed
- 2026-06-16: patched: Fix released in v2.3.3 and v2.2.3

## References

- [https://github.com/crossplane/crossplane-runtime/security/advisories/GHSA-mf7q-r4rv-jv94](https://github.com/crossplane/crossplane-runtime/security/advisories/GHSA-mf7q-r4rv-jv94)
- [https://github.com/crossplane/crossplane-runtime/pull/1038](https://github.com/crossplane/crossplane-runtime/pull/1038)

## Related threats

- [Crossplane crossplane-runtime time-of-check time-of-use in package verification](https://junglewise.ai/threats/cve-2026-105163-a-vulnerability-was-detected-in-crossplane-crossplane-runtime-up)
- [Crossplane package manager signature bypass via TOCTOU in tag resolution](https://junglewise.ai/threats/crossplane-package-manager-signature-bypass-via-toctou-in-tag-c3cd8716)