Executive brief
Crossplane is an open-source framework used to manage cloud infrastructure. A security flaw in how it verifies software packages allows a malicious registry to bypass security checks. This could result in the installation of unverified or malicious software onto your infrastructure, potentially leading to a full system compromise or data theft.
Technical details
A Time-of-Check Time-of-Use (TOCTOU) vulnerability exists in Crossplane's package manager when signature verification is enabled via ImageConfig. When a package is installed using a mutable tag (e.g., a version number) rather than a static digest, Crossplane performs two separate resolution steps: one for signature verification using cosign and another for the actual image pull. A malicious OCI registry can exploit this by serving a valid, signed image during the verification phase and then swapping it for an unsigned, malicious image during the installation phase. This bypasses the security guarantees of signature verification. The fix ensures that the tag is resolved to a digest once and that same digest is used for both verification and fetching.
Affected products
- Crossplane Crossplane <= 1.21.0-rc.0
- Crossplane Crossplane >= 2.3.0-rc.0, <= 2.3.2
- Crossplane Crossplane <= 2.2.2
Timeline
- 2026-06-16: disclosed: Advisory published to crossplane/crossplane repository
- 2026-06-19: advisory: GitHub Advisory published and reviewed
References
- https://api.github.com/users/bugbunny-research
- https://github.com/bugbunny-research
- https://api.github.com/users/bugbunny-research/gists%7B/gist_id%7D
- https://api.github.com/users/bugbunny-research/repos
- https://avatars.githubusercontent.com/u/262839898?v=4
- https://api.github.com/users/bugbunny-research/events%7B/privacy%7D