CVE-2026-40923

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:

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.

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.

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

Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.

CVE-2026-40923 has a CVSS score of 5.4 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.11.1, 1.9.3, 1.6.2, 1.3.4, 1.0.2); upgrading removes the vulnerable code path.

Kodem intelligence

(to be filled: fixed in versions X.Y.Z)

1. What is CVE-2026-40923? CVE-2026-40923 is a medium-severity path traversal vulnerability in github.com/tektoncd/pipeline (go), affecting versions >= 1.10.0, < 1.11.1. It is fixed in 1.11.1, 1.9.3, 1.6.2, 1.3.4, 1.0.2. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
2. How severe is CVE-2026-40923? CVE-2026-40923 has a CVSS score of 5.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/tektoncd/pipeline are affected by CVE-2026-40923? github.com/tektoncd/pipeline (go) versions >= 1.10.0, < 1.11.1 is affected.
4. Is there a fix for CVE-2026-40923? Yes. CVE-2026-40923 is fixed in 1.11.1, 1.9.3, 1.6.2, 1.3.4, 1.0.2. Upgrade to this version or later.
5. Is CVE-2026-40923 exploitable, and should I be worried? Whether CVE-2026-40923 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-40923 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-40923?
   • Upgrade github.com/tektoncd/pipeline to 1.11.1 or later
   • Upgrade github.com/tektoncd/pipeline to 1.9.3 or later
   • Upgrade github.com/tektoncd/pipeline to 1.6.2 or later
   • Upgrade github.com/tektoncd/pipeline to 1.3.4 or later
   • Upgrade github.com/tektoncd/pipeline to 1.0.2 or later