GHSA-rx35-6rhx-7858 Tekton Pipelines: VolumeMount path restriction bypass via missing filepath.Clean in /tekton/ check

• Go github.com/tektoncd/pipeline: >= 1.10.0, < 1.11.1 → fixed in 1.11.1 • Go github.com/tektoncd/pipeline: >= 1.7.0, < 1.9.3 → fixed in 1.9.3 • Go github.com/tektoncd/pipeline: >= 1.4.0, < 1.6.2 → fixed in 1.6.2 • Go github.com/tektoncd/pipeline: >= 1.2.0, < 1.3.4 → fixed in 1.3.4 • Go github.com/tektoncd/pipeline: >= 1.0.0, < 1.0.2 → fixed in 1.0.2

Summary A validation bypass in the VolumeMount path restriction allows mounting volumes under restricted `/tekton/` internal paths by using `..` path traversal components. The restriction check uses `strings.HasPrefix` without `filepath.Clean`, so a path like `/tekton/home/../results` passes validation but resolves to `/tekton/results` at runtime. Details Tekton Pipelines restricts VolumeMount paths under `/tekton/` (except `/tekton/home`) to prevent users from interfering with internal execution state. The validation at `pkg/apis/pipeline/v1/container_validation.go` checks mount paths using `strings.HasPrefix` without normalizing the path first: ```go if strings.HasPrefix(vm.MountPath, "/tekton/") && !strings.HasPrefix(vm.MountPath, "/tekton/home") { // reject } ``` Because `/tekton/home` is an allowed prefix, a path like `/tekton/home/../results` passes both checks. At runtime, the container runtime resolves `..` and the actual mount point becomes `/tekton/results`. The same pattern exists in `pkg/apis/pipeline/v1beta1/task_validation.go`. Impact An authenticated user with Task or TaskRun creation permissions can mount volumes over internal Tekton paths, potentially: • Writing fake task results that downstream pipelines trust • Reading or modifying step scripts before execution • Interfering with entrypoint coordination state Patches _(to be filled: fixed in versions X.Y.Z)_ Workarounds • Use admission controllers (OPA/Gatekeeper, Kyverno) to validate that VolumeMount paths do not contain `..` components. • In multi-tenant setups, restrict who can create Task and TaskRun resources via RBAC. Affected Versions All versions through v1.10.0 (both `v1` and `v1beta1` APIs). Acknowledgments This vulnerability was reported by @kodareef5.