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Tekton Pipelines VolumeMount path restriction validation bypass
CVE-2026-40923 affects Tekton Pipelines starting in version 1.0.0 and before fixed releases 1.0.2, 1.3.4, 1.6.2, 1.9.3, and 1.11.1. The vulnerability is a validation bypass in the VolumeMount mountPath restriction logic for protected internal /tekton/ paths. The validation checks mount paths using strings.HasPrefix but does not normalize the path with filepath.Clean before evaluating it. As a result, a crafted mountPath such as /tekton/home/../results can satisfy the prefix-based validation while resolving at runtime to a different restricted internal path such as /tekton/results. This allows an attacker to use .. path traversal components to mount volumes under internal Tekton paths that should be blocked. The issue is fixed by adding filepath.Clean-based path normalization in the admission webhook validation path.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
Successful exploitation allows a user who can submit Tekton Task or TaskRun definitions to mount attacker-controlled volumes over restricted internal Tekton directories. According to the provided advisory context, this can enable writing forged task results that may be trusted by downstream pipeline logic, reading or modifying step scripts before execution, and interfering with Tekton entrypoint coordination state. Depending on pipeline design and trust assumptions, this can compromise CI/CD integrity, tamper with build or execution outcomes, expose sensitive workflow data, and disrupt pipeline execution.
If you can’t patch tonight, do this now.
If immediate upgrade is not possible, deploy compensating admission controls to reject malicious Task and TaskRun objects containing path traversal in VolumeMount.mountPath, especially '..' sequences. The provided content specifically recommends Kubernetes Validating Admission Policies, OPA Gatekeeper, or Kyverno for this purpose. As additional risk reduction, audit and tighten RBAC so that only trusted CI/CD service accounts and authorized personnel can create Task, TaskRun, Pipeline, and PipelineRun resources, and restrict namespace access to reduce blast radius in multi-tenant environments.
Patch, then assume compromise.
Upgrade Tekton Pipelines to a fixed release on the relevant supported branch. Fixed versions identified in the provided content are 1.0.2, 1.3.4, 1.6.2, 1.9.3, and 1.11.1. The definitive remediation called out in the content is upgrading the deployment to 1.11.1 or later, which incorporates filepath.Clean logic into the admission webhooks to ensure proper path normalization before enforcing mount path restrictions. Deploy the updated Tekton Pipelines manifests using standard Kubernetes lifecycle management procedures.
No public exploits tracked yet. Mallory keeps watching.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
3 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.