diff --git a/README.md b/README.md
index ebb45f8d..7e32e7d8 100644
--- a/README.md
+++ b/README.md
@@ -355,7 +355,6 @@ The following tests are not yet implemented and therefore missing:
 - Recommended Test 6.2.32
 - Recommended Test 6.2.33
 - Recommended Test 6.2.34
-- Recommended Test 6.2.35
 - Recommended Test 6.2.36
 - Recommended Test 6.2.37
 - Recommended Test 6.2.38
@@ -462,6 +461,7 @@ export const recommendedTest_6_2_16: DocumentTest
 export const recommendedTest_6_2_17: DocumentTest
 export const recommendedTest_6_2_18: DocumentTest
 export const recommendedTest_6_2_22: DocumentTest
+export const recommendedTest_6_2_35: DocumentTest
 ```
 
 [(back to top)](#bsi-csaf-validator-lib)
diff --git a/csaf_2_1/recommendedTests.js b/csaf_2_1/recommendedTests.js
index aeb25c42..2ddb3f5c 100644
--- a/csaf_2_1/recommendedTests.js
+++ b/csaf_2_1/recommendedTests.js
@@ -30,4 +30,5 @@ export { recommendedTest_6_2_22 } from './recommendedTests/recommendedTest_6_2_2
 export { recommendedTest_6_2_27 } from './recommendedTests/recommendedTest_6_2_27.js'
 export { recommendedTest_6_2_28 } from './recommendedTests/recommendedTest_6_2_28.js'
 export { recommendedTest_6_2_29 } from './recommendedTests/recommendedTest_6_2_29.js'
+export { recommendedTest_6_2_35 } from './recommendedTests/recommendedTest_6_2_35.js'
 export { recommendedTest_6_2_38 } from './recommendedTests/recommendedTest_6_2_38.js'
diff --git a/csaf_2_1/recommendedTests/recommendedTest_6_2_35.js b/csaf_2_1/recommendedTests/recommendedTest_6_2_35.js
new file mode 100644
index 00000000..f75c90bf
--- /dev/null
+++ b/csaf_2_1/recommendedTests/recommendedTest_6_2_35.js
@@ -0,0 +1,100 @@
+import Ajv from 'ajv/dist/jtd.js'
+
+const ajv = new Ajv()
+
+const inputSchema = /** @type {const} */ ({
+  additionalProperties: true,
+  properties: {
+    document: {
+      additionalProperties: true,
+      properties: {
+        distribution: {
+          additionalProperties: true,
+          properties: {
+            tlp: {
+              additionalProperties: true,
+              properties: {
+                label: { type: 'string' },
+              },
+            },
+          },
+        },
+      },
+    },
+    vulnerabilities: {
+      elements: {
+        additionalProperties: true,
+        optionalProperties: {
+          metrics: {
+            elements: {
+              additionalProperties: true,
+              optionalProperties: {
+                content: {
+                  additionalProperties: true,
+                  optionalProperties: {
+                    ssvc_v1: {
+                      additionalProperties: true,
+                      optionalProperties: {
+                        selections: {
+                          elements: {
+                            additionalProperties: true,
+                            optionalProperties: {
+                              namespace: {
+                                type: 'string',
+                              },
+                            },
+                          },
+                        },
+                      },
+                    },
+                  },
+                },
+              },
+            },
+          },
+        },
+      },
+    },
+  },
+})
+
+const validate = ajv.compile(inputSchema)
+
+/**
+ * This implements the recommended test 6.2.35 of the CSAF 2.1 standard.
+ *
+ * @param {any} doc
+ */
+export function recommendedTest_6_2_35(doc) {
+  /** @type {Array<{ message: string; instancePath: string }>} */
+  const warnings = []
+  const context = { warnings }
+
+  if (!validate(doc)) {
+    return context
+  }
+
+  /*
+   * According to https://certcc.github.io/SSVC/data/schema/v1/Decision_Point-1-0-1.schema.json#/$defs/decision_point/properties/namespace
+   * a private namespace starts with "x_"
+   * */
+
+  if (doc.document.distribution.tlp.label !== 'CLEAR') {
+    return context
+  }
+  doc.vulnerabilities?.forEach((vulnerability, vulnerabilityIndex) => {
+    vulnerability.metrics?.forEach((metric, metricIndex) => {
+      const selections = metric.content?.ssvc_v1?.selections || []
+      selections.forEach((selection, selectionIndex) => {
+        if (selection.namespace?.startsWith('x_')) {
+          context.warnings.push({
+            message: `The namespace "${selection.namespace}" is a private namespace`,
+            instancePath: `/vulnerabilities/${vulnerabilityIndex}/metrics/${metricIndex}/content/ssvc_v1/selections/${selectionIndex}/namespace`,
+          })
+        }
+      })
+    })
+  })
+
+  return context
+}
diff --git a/tests/csaf_2_1/oasis.js b/tests/csaf_2_1/oasis.js
index 31ce644c..569a0c9d 100644
--- a/tests/csaf_2_1/oasis.js
+++ b/tests/csaf_2_1/oasis.js
@@ -53,7 +53,6 @@ const excluded = [
   '6.2.32',
   '6.2.33',
   '6.2.34',
-  '6.2.35',
   '6.2.36',
   '6.2.37',
   '6.2.39.1',
diff --git a/tests/csaf_2_1/recommendedTest_6_2_35.js b/tests/csaf_2_1/recommendedTest_6_2_35.js
new file mode 100644
index 00000000..c07c4cdd
--- /dev/null
+++ b/tests/csaf_2_1/recommendedTest_6_2_35.js
@@ -0,0 +1,51 @@
+import assert from 'node:assert'
+import { recommendedTest_6_2_35 } from '../../csaf_2_1/recommendedTests.js'
+
+describe('recommendedTest_6_2_35', function () {
+  it('only runs on relevant documents', function () {
+    assert.equal(
+      recommendedTest_6_2_35({ vulnerabilities: 'mydoc' }).warnings.length,
+      0
+    )
+  })
+  it('skips empty objects', function () {
+    assert.equal(
+      recommendedTest_6_2_35({
+        document: {
+          distribution: {
+            tlp: {
+              label: 'CLEAR',
+            },
+          },
+        },
+        vulnerabilities: [
+          {
+            metrics: [
+              {
+                content: {
+                  ssvc_v1: {}, // should be ignored
+                },
+              },
+            ],
+          },
+          {
+            metrics: [
+              {
+                content: {
+                  ssvc_v1: {
+                    selections: [
+                      {
+                        namespace: 'x_custom',
+                      },
+                    ],
+                  },
+                },
+              },
+            ],
+          },
+        ],
+      }).warnings.length,
+      1
+    )
+  })
+})