Executive brief
### Impact Insufficient validation of Git URL fragment subdir components (`<url>#<ref>:<subdir>`, [docs](https://docs.docker.com/build/concepts/context/#url-fragments)) may allow access to files outside the checked-out Git repository root. Possible access is limited to files on the same mounted filesystem.
### Patches The issue has been fixed in version v0.28.1
### Workarounds The issue affects only builds that use Git URLs with a subpath component. Avoid building Dockerfiles from untrusted sources or using the subdir component from an untrusted Git repository where the subdir component could point to a symlink.
Affected products
- go github.com/moby/buildkit