diff --git a/README.md b/README.md
index 06f06622..194be7cc 100644
--- a/README.md
+++ b/README.md
@@ -336,7 +336,6 @@ 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
@@ -495,6 +494,7 @@ export const recommendedTest_6_2_27: DocumentTest
 export const recommendedTest_6_2_28: DocumentTest
 export const recommendedTest_6_2_29: DocumentTest
 export const recommendedTest_6_2_30: DocumentTest
+export const recommendedTest_6_2_35: DocumentTest
 export const recommendedTest_6_2_39_2: DocumentTest
 export const recommendedTest_6_2_39_3: DocumentTest
 export const recommendedTest_6_2_39_4: DocumentTest
diff --git a/csaf_2_1/recommendedTests.js b/csaf_2_1/recommendedTests.js
index 46213ccb..6e3679a5 100644
--- a/csaf_2_1/recommendedTests.js
+++ b/csaf_2_1/recommendedTests.js
@@ -33,6 +33,7 @@ export { recommendedTest_6_2_27 } from './recommendedTests/recommendedTest_6_2_2
 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_30 } from './recommendedTests/recommendedTest_6_2_30.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'
 export { recommendedTest_6_2_39_2 } from './recommendedTests/recommendedTest_6_2_39_2.js'
 export { recommendedTest_6_2_39_3 } from './recommendedTests/recommendedTest_6_2_39_3.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..d3da099c
--- /dev/null
+++ b/csaf_2_1/recommendedTests/recommendedTest_6_2_35.js
@@ -0,0 +1,106 @@
+import { Ajv } from 'ajv/dist/jtd.js'
+import {
+  isSpecialPurposeSsvcNamespace,
+  isUnregisteredNamespace,
+} from '../shared/ssvcNamespaces.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_v2: {
+                      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
+  }
+
+  if (doc.document.distribution.tlp.label !== 'CLEAR') {
+    return context
+  }
+  doc.vulnerabilities?.forEach((vulnerability, vulnerabilityIndex) => {
+    vulnerability.metrics?.forEach((metric, metricIndex) => {
+      const selections = metric.content?.ssvc_v2?.selections || []
+      selections.forEach((selection, selectionIndex) => {
+        if (!selection?.namespace) return
+        const instancePath = `/vulnerabilities/${vulnerabilityIndex}/metrics/${metricIndex}/content/ssvc_v2/selections/${selectionIndex}/namespace`
+        if (isSpecialPurposeSsvcNamespace(selection.namespace)) {
+          context.warnings.push({
+            message: `The namespace "${selection.namespace}" is reserved for special purpose (documentation/testing) and must not be used in production`,
+            instancePath,
+          })
+        } else if (isUnregisteredNamespace(selection.namespace)) {
+          context.warnings.push({
+            message: `The namespace "${selection.namespace}" is an unregistered namespace`,
+            instancePath,
+          })
+        }
+      })
+    })
+  })
+
+  return context
+}
diff --git a/csaf_2_1/shared/ssvcNamespaces.js b/csaf_2_1/shared/ssvcNamespaces.js
new file mode 100644
index 00000000..65762f24
--- /dev/null
+++ b/csaf_2_1/shared/ssvcNamespaces.js
@@ -0,0 +1,59 @@
+/**
+ * SSVC Namespace Specification: https://certcc.github.io/SSVC/reference/code/namespaces/
+ *
+ * Namespaces reserved for special purpose and MUST be treated as per their
+ * definition (spec section "Reserved Namespace Strings").
+ *
+ * @type {string[]}
+ */
+export const specialPurposeSsvcNamespaces = ['x_example', 'x_test']
+
+/**
+ * Extracts the base namespace from a full SSVC namespace string.
+ * Strips everything after the first '#' or '/'.
+ *
+ * @param {string} namespace
+ * @returns {string}
+ */
+export function getSsvcBaseNamespace(namespace) {
+  const hashIdx = namespace.indexOf('#')
+  const slashIdx = namespace.indexOf('/')
+
+  let endIdx = namespace.length
+  if (hashIdx !== -1) endIdx = Math.min(endIdx, hashIdx)
+  if (slashIdx !== -1) endIdx = Math.min(endIdx, slashIdx)
+
+  return namespace.substring(0, endIdx)
+}
+
+/**
+ * Returns true if the namespace is a valid unregistered SSVC namespace.
+ *
+ * Unregistered namespaces must:
+ * - start with the `x_` prefix
+ * - followed by a reverse domain name (alphanumeric, dots, dashes)
+ * - followed by `#` and a non-empty fragment
+ * - contain only alphanumeric characters, dots (.), and dashes (-) besides `x_` and `#`
+ *
+ * @param {string} namespace - full namespace string
+ * @returns {boolean}
+ */
+export function isUnregisteredNamespace(namespace) {
+  // x_ + one or more labels (dot-separated) + optional #fragment
+  return /^x_[a-zA-Z0-9-]+(\.[a-zA-Z0-9-]+)*(#[a-zA-Z0-9.\-]+)?$/.test(
+    namespace
+  )
+}
+
+/**
+ * Returns true if the namespace uses a reserved special-purpose prefix
+ * (x_example or x_test). These namespaces are valid structurally but must
+ * not be used in production.
+ *
+ * @param {string} namespace - full namespace string
+ * @returns {boolean}
+ */
+export function isSpecialPurposeSsvcNamespace(namespace) {
+  const base = getSsvcBaseNamespace(namespace)
+  return specialPurposeSsvcNamespaces.some((prefix) => base === prefix)
+}
diff --git a/tests/csaf_2_1/oasis.js b/tests/csaf_2_1/oasis.js
index 749b831e..cb39dc01 100644
--- a/tests/csaf_2_1/oasis.js
+++ b/tests/csaf_2_1/oasis.js
@@ -38,7 +38,6 @@ 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..2da52cb0
--- /dev/null
+++ b/tests/csaf_2_1/recommendedTest_6_2_35.js
@@ -0,0 +1,185 @@
+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_v2: {}, // should be ignored
+                },
+              },
+            ],
+          },
+          {
+            metrics: [
+              {
+                content: {
+                  ssvc_v2: {
+                    selections: [
+                      {
+                        namespace: 'x_com.example#custom',
+                      },
+                    ],
+                  },
+                },
+              },
+            ],
+          },
+        ],
+      }).warnings.length,
+      1
+    )
+  })
+
+  it('skips selections without a namespace', function () {
+    assert.equal(
+      recommendedTest_6_2_35({
+        document: {
+          distribution: { tlp: { label: 'CLEAR' } },
+        },
+        vulnerabilities: [
+          {
+            metrics: [
+              {
+                content: {
+                  ssvc_v2: {
+                    selections: [{}, { namespace: '' }],
+                  },
+                },
+              },
+            ],
+          },
+        ],
+      }).warnings.length,
+      0
+    )
+  })
+
+  it('warns for special purpose namespaces', function () {
+    assert.equal(
+      recommendedTest_6_2_35({
+        document: {
+          distribution: { tlp: { label: 'CLEAR' } },
+        },
+        vulnerabilities: [
+          {
+            metrics: [
+              {
+                content: {
+                  ssvc_v2: {
+                    selections: [
+                      { namespace: 'x_example#test' },
+                      { namespace: 'x_test#ref' },
+                    ],
+                  },
+                },
+              },
+            ],
+          },
+        ],
+      }).warnings.length,
+      2
+    )
+  })
+
+  it('warns for unregistered namespaces that look like special purpose (x_example.something)', function () {
+    const result = recommendedTest_6_2_35({
+      document: {
+        distribution: { tlp: { label: 'CLEAR' } },
+      },
+      vulnerabilities: [
+        {
+          metrics: [
+            {
+              content: {
+                ssvc_v2: {
+                  selections: [
+                    { namespace: 'x_example.unregistered#namespace' },
+                    { namespace: 'x_test.org#ref' },
+                  ],
+                },
+              },
+            },
+          ],
+        },
+      ],
+    })
+    assert.equal(result.warnings.length, 2)
+    assert.ok(
+      result.warnings.every((w) =>
+        w.message.includes('unregistered namespace')
+      ),
+      'expected "unregistered namespace" message for x_example.something and x_test.org forms'
+    )
+  })
+
+  it('warns for single-label unregistered namespace without dot (x_somedomain#fragment)', function () {
+    const result = recommendedTest_6_2_35({
+      document: {
+        distribution: { tlp: { label: 'CLEAR' } },
+      },
+      vulnerabilities: [
+        {
+          metrics: [
+            {
+              content: {
+                ssvc_v2: {
+                  selections: [{ namespace: 'x_somedomain#fragment' }],
+                },
+              },
+            },
+          ],
+        },
+      ],
+    })
+    assert.equal(result.warnings.length, 1)
+    assert.ok(
+      result.warnings[0].message.includes('unregistered namespace'),
+      'expected "unregistered namespace" message for x_somedomain#fragment'
+    )
+  })
+
+  it('warns for fragment-free unregistered namespace (x_com.example)', function () {
+    const result = recommendedTest_6_2_35({
+      document: {
+        distribution: { tlp: { label: 'CLEAR' } },
+      },
+      vulnerabilities: [
+        {
+          metrics: [
+            {
+              content: {
+                ssvc_v2: {
+                  selections: [{ namespace: 'x_com.example' }],
+                },
+              },
+            },
+          ],
+        },
+      ],
+    })
+    assert.equal(result.warnings.length, 1)
+    assert.ok(
+      result.warnings[0].message.includes('unregistered namespace'),
+      'expected "unregistered namespace" message for x_com.example (no fragment)'
+    )
+  })
+})