CVE-2026-40923: Tekton Pipelines VolumeMount Path Restriction Bypass Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-rx35-6rhx-7858",
  "modified" : "2026-05-22T15:40:40Z",
  "published" : "2026-04-21T20:26:41Z",
  "aliases" : [ "CVE-2026-40923" ],
  "summary" : "Tekton Pipelines: VolumeMount path restriction bypass via missing filepath.Clean in /tekton/ check",
  "details" : "### Summary\n\nA validation bypass in the VolumeMount path restriction allows mounting\nvolumes under restricted `/tekton/` internal paths by using `..` path\ntraversal components. The restriction check uses `strings.HasPrefix`\nwithout `filepath.Clean`, so a path like `/tekton/home/../results`\npasses validation but resolves to `/tekton/results` at runtime.\n\n### Details\n\nTekton Pipelines restricts VolumeMount paths under `/tekton/` (except\n`/tekton/home`) to prevent users from interfering with internal\nexecution state. The validation at\n`pkg/apis/pipeline/v1/container_validation.go` checks mount paths using\n`strings.HasPrefix` without normalizing the path first:\n\n```go\nif strings.HasPrefix(vm.MountPath, \"/tekton/\") &&\n    !strings.HasPrefix(vm.MountPath, \"/tekton/home\") {\n    // reject\n}\n```\n\nBecause `/tekton/home` is an allowed prefix, a path like\n`/tekton/home/../results` passes both checks. At runtime, the container\nruntime resolves `..` and the actual mount point becomes\n`/tekton/results`.\n\nThe same pattern exists in `pkg/apis/pipeline/v1beta1/task_validation.go`.\n\n### Impact\n\nAn authenticated user with Task or TaskRun creation permissions can\nmount volumes over internal Tekton paths, potentially:\n\n- Writing fake task results that downstream pipelines trust\n- Reading or modifying step scripts before execution\n- Interfering with entrypoint coordination state\n\n### Patches\n\n_(to be filled: fixed in versions X.Y.Z)_\n\n### Workarounds\n\n- Use admission controllers (OPA/Gatekeeper, Kyverno) to validate that\n  VolumeMount paths do not contain `..` components.\n- In multi-tenant setups, restrict who can create Task and TaskRun\n  resources via RBAC.\n\n### Affected Versions\n\nAll versions through **v1.10.0** (both `v1` and `v1beta1` APIs).\n\n### Acknowledgments\n\nThis vulnerability was reported by @kodareef5.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/tektoncd/pipeline"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.10.0"
      }, {
        "fixed" : "1.11.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/tektoncd/pipeline"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.7.0"
      }, {
        "fixed" : "1.9.3"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/tektoncd/pipeline"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.4.0"
      }, {
        "fixed" : "1.6.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/tektoncd/pipeline"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.2.0"
      }, {
        "fixed" : "1.3.4"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/tektoncd/pipeline"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.0.0"
      }, {
        "fixed" : "1.0.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/tektoncd/pipeline/security/advisories/GHSA-rx35-6rhx-7858"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-40923"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/tektoncd/pipeline"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/tektoncd/pipeline/releases/tag/v1.11.1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-21T20:26:41Z",
    "nvd_published_at" : "2026-04-21T21:16:45Z"
  }
}