diff --git a/csaf_2_1/mandatoryTests.js b/csaf_2_1/mandatoryTests.js
index 60b53fd3..bc409301 100644
--- a/csaf_2_1/mandatoryTests.js
+++ b/csaf_2_1/mandatoryTests.js
@@ -20,7 +20,6 @@ export {
   mandatoryTest_6_1_27_2,
   mandatoryTest_6_1_27_6,
   mandatoryTest_6_1_27_7,
-  mandatoryTest_6_1_27_8,
   mandatoryTest_6_1_27_9,
   mandatoryTest_6_1_27_10,
   mandatoryTest_6_1_28,
@@ -42,6 +41,7 @@ export { mandatoryTest_6_1_13 } from './mandatoryTests/mandatoryTest_6_1_13.js'
 export { mandatoryTest_6_1_27_3 } from './mandatoryTests/mandatoryTest_6_1_27_3.js'
 export { mandatoryTest_6_1_27_4 } from './mandatoryTests/mandatoryTest_6_1_27_4.js'
 export { mandatoryTest_6_1_27_5 } from './mandatoryTests/mandatoryTest_6_1_27_5.js'
+export { mandatoryTest_6_1_27_8 } from './mandatoryTests/mandatoryTest_6_1_27_8.js'
 export { mandatoryTest_6_1_27_11 } from './mandatoryTests/mandatoryTest_6_1_27_11.js'
 export { mandatoryTest_6_1_27_12 } from './mandatoryTests/mandatoryTest_6_1_27_12.js'
 export { mandatoryTest_6_1_27_14 } from './mandatoryTests/mandatoryTest_6_1_27_14.js'
diff --git a/csaf_2_1/mandatoryTests/mandatoryTest_6_1_27_8.js b/csaf_2_1/mandatoryTests/mandatoryTest_6_1_27_8.js
new file mode 100644
index 00000000..7f474c17
--- /dev/null
+++ b/csaf_2_1/mandatoryTests/mandatoryTest_6_1_27_8.js
@@ -0,0 +1,206 @@
+import { Ajv } from 'ajv/dist/jtd.js'
+
+const ajv = new Ajv()
+
+/*
+  This is the jtd schema that needs to match the input document so that the
+  test is activated. If this schema doesn't match it normally means that the input
+  document does not validate against the csaf json schema or optional fields that
+  the test checks are not present.
+ */
+const inputSchema = /** @type {const} */ ({
+  additionalProperties: true,
+  properties: {
+    document: {
+      additionalProperties: true,
+      properties: {
+        category: {
+          type: 'string',
+        },
+      },
+    },
+    vulnerabilities: {
+      elements: {
+        additionalProperties: true,
+        optionalProperties: {
+          cve: { type: 'string' },
+          ids: {
+            elements: {
+              additionalProperties: true,
+              optionalProperties: {
+                product_ids: { elements: { type: 'string' } },
+                group_ids: { elements: { type: 'string' } },
+              },
+            },
+          },
+        },
+      },
+    },
+  },
+  optionalProperties: {
+    product_tree: {
+      additionalProperties: true,
+      optionalProperties: {
+        product_groups: {
+          elements: {
+            additionalProperties: true,
+            optionalProperties: {
+              group_id: { type: 'string' },
+              product_ids: { elements: { type: 'string' } },
+            },
+          },
+        },
+      },
+    },
+  },
+})
+
+const validate = ajv.compile(inputSchema)
+
+/** @typedef {import('ajv/dist/jtd.js').JTDDataType<typeof inputSchema>} InputDoc */
+/** @typedef {InputDoc['vulnerabilities'][number]} Vulnerability */
+/** @typedef {NonNullable<Vulnerability['ids']>[number]} VulnerabilityId */
+/** @typedef {NonNullable<NonNullable<InputDoc['product_tree']>['product_groups']>[number]} ProductGroup */
+
+/**
+ * This implements the mandatory test 6.1.27.8 of the CSAF 2.1 standard.
+ *
+ * @param {unknown} doc
+ */
+export function mandatoryTest_6_1_27_8(doc) {
+  /** @type {Array<{ message: string; instancePath: string }>} */
+  const errors = []
+  let isValid = true
+
+  if (!validate(doc) || doc.document.category !== 'csaf_vex') {
+    return { errors, isValid }
+  }
+
+  /** @type {Map<string, Set<string>>} */
+  const groupProductMap = new Map()
+  /** @type {ProductGroup[] | undefined} */
+  const productGroups = doc.product_tree?.product_groups
+  if (Array.isArray(productGroups)) {
+    for (const group of productGroups) {
+      if (
+        typeof group.group_id === 'string' &&
+        Array.isArray(group.product_ids)
+      ) {
+        groupProductMap.set(group.group_id, new Set(group.product_ids))
+      }
+    }
+  }
+
+  /** @type {Vulnerability[]} */
+  const vulnerabilities = doc.vulnerabilities
+  if (Array.isArray(vulnerabilities)) {
+    vulnerabilities.forEach((vulnerability, vulnerabilityIndex) => {
+      if (['ids', 'cve'].every((p) => vulnerability[p] === undefined)) {
+        isValid = false
+        errors.push({
+          instancePath: `/vulnerabilities/${vulnerabilityIndex}`,
+          message:
+            'Neither a CVE nor a general vulnerability id (ids) is given for this vulnerability.',
+        })
+        return
+      }
+
+      if (vulnerability.cve !== undefined) return
+
+      if (!Array.isArray(vulnerability.ids)) return
+
+      const allScoped = vulnerability.ids.every(
+        (id) =>
+          (Array.isArray(id.product_ids) && id.product_ids.length > 0) ||
+          (Array.isArray(id.group_ids) && id.group_ids.length > 0)
+      )
+      if (!allScoped) return
+
+      const coveredProducts = getAllCoveredProducts(
+        vulnerability.ids,
+        groupProductMap
+      )
+
+      const productStatus =
+        /** @type {Record<string, unknown> | null | undefined} */ (
+          vulnerability.product_status
+        )
+      if (productStatus == null || typeof productStatus !== 'object') return
+
+      const hadErrors = checkProductStatus(
+        productStatus,
+        coveredProducts,
+        vulnerabilityIndex,
+        errors
+      )
+      if (hadErrors) {
+        isValid = false
+      }
+    })
+  }
+
+  return { errors, isValid }
+}
+
+/**
+ * Collects all product ids covered by the given ids entries,
+ * resolving group_ids via groupProductMap.
+ * @param {VulnerabilityId[]} ids
+ * @param {Map<string, Set<string>>} groupProductMap
+ * @returns {Set<string>}
+ */
+function getAllCoveredProducts(ids, groupProductMap) {
+  const coveredProducts = new Set()
+  for (const id of ids) {
+    if (Array.isArray(id.product_ids)) {
+      for (const pid of id.product_ids) {
+        coveredProducts.add(pid)
+      }
+    }
+    if (Array.isArray(id.group_ids)) {
+      for (const gid of id.group_ids) {
+        const members = groupProductMap.get(gid)
+        if (members) {
+          for (const pid of members) {
+            coveredProducts.add(pid)
+          }
+        }
+      }
+    }
+  }
+  return coveredProducts
+}
+
+/**
+ * Checks that every product referenced in product_status is covered.
+ * Returns true if any uncovered products were found.
+ * @param {Record<string, unknown>} productStatus
+ * @param {Set<string>} coveredProducts
+ * @param {number} vulnerabilityIndex
+ * @param {Array<{ message: string; instancePath: string }>} errors
+ * @returns {boolean}
+ */
+function checkProductStatus(
+  productStatus,
+  coveredProducts,
+  vulnerabilityIndex,
+  errors
+) {
+  let hadErrors = false
+  for (const [statusKey, productIds] of Object.entries(productStatus)) {
+    if (!Array.isArray(productIds)) continue
+    productIds.forEach((productId, productIdIndex) => {
+      if (typeof productId !== 'string') return
+      if (!coveredProducts.has(productId)) {
+        hadErrors = true
+        errors.push({
+          instancePath: `/vulnerabilities/${vulnerabilityIndex}/product_status/${statusKey}/${productIdIndex}`,
+          message:
+            `product id \`${productId}\` does not have a vulnerability id assigned` +
+            ` nor a CVE or general vulnerability id is given`,
+        })
+      }
+    })
+  }
+  return hadErrors
+}
diff --git a/tests/csaf_2_1/mandatoryTest_6_1_27_8.js b/tests/csaf_2_1/mandatoryTest_6_1_27_8.js
new file mode 100644
index 00000000..79a65395
--- /dev/null
+++ b/tests/csaf_2_1/mandatoryTest_6_1_27_8.js
@@ -0,0 +1,94 @@
+import assert from 'node:assert/strict'
+import { mandatoryTest_6_1_27_8 } from '../../csaf_2_1/mandatoryTests/mandatoryTest_6_1_27_8.js'
+
+describe('mandatoryTest_6_1_27_8', function () {
+  it('only runs on relevant documents (skips non-object document)', function () {
+    assert.equal(mandatoryTest_6_1_27_8({ document: 'mydoc' }).isValid, true)
+  })
+
+  it('returns valid for documents with irrelevant category', function () {
+    assert.equal(
+      mandatoryTest_6_1_27_8({
+        document: { category: 'csaf_base' },
+        vulnerabilities: [{ title: 'no cve, no ids' }],
+      }).isValid,
+      true
+    )
+  })
+
+  it('reports uncovered products when vulnerability has empty ids array', function () {
+    const result = mandatoryTest_6_1_27_8({
+      document: { category: 'csaf_vex' },
+      vulnerabilities: [
+        {
+          ids: [],
+          product_status: { known_affected: ['PROD_A'] },
+        },
+      ],
+    })
+    assert.equal(result.isValid, false)
+    assert.equal(result.errors.length, 1)
+    assert.equal(
+      result.errors[0].instancePath,
+      '/vulnerabilities/0/product_status/known_affected/0'
+    )
+  })
+
+  it('returns valid when product_status is absent (nothing to check)', function () {
+    const result = mandatoryTest_6_1_27_8({
+      document: { category: 'csaf_vex' },
+      vulnerabilities: [
+        {
+          ids: [
+            {
+              system_name: 'Tracking System',
+              text: 'TRACK-001',
+              product_ids: ['PROD_A'],
+            },
+          ],
+        },
+      ],
+    })
+    assert.equal(result.isValid, true)
+    assert.equal(result.errors.length, 0)
+  })
+
+  it('skips non-array product_status entries (e.g. a string value)', function () {
+    const result = mandatoryTest_6_1_27_8({
+      document: { category: 'csaf_vex' },
+      vulnerabilities: [
+        {
+          ids: [
+            {
+              system_name: 'Tracking System',
+              text: 'TRACK-001',
+              product_ids: ['PROD_A'],
+            },
+          ],
+          product_status: { known_affected: 'not-an-array' },
+        },
+      ],
+    })
+    assert.equal(result.isValid, true)
+    assert.equal(result.errors.length, 0)
+  })
+
+  it('skips non-string product ids in product_status', function () {
+    const result = mandatoryTest_6_1_27_8({
+      document: { category: 'csaf_vex' },
+      vulnerabilities: [
+        {
+          ids: [
+            {
+              system_name: 'Tracking System',
+              text: 'TRACK-001',
+              product_ids: ['PROD_A'],
+            },
+          ],
+          product_status: { known_affected: [42, null, 'PROD_B'] },
+        },
+      ],
+    })
+    assert.equal(result.errors.length, 1)
+  })
+})
diff --git a/tests/csaf_2_1/oasis.js b/tests/csaf_2_1/oasis.js
index 51e4d5bc..c0448b30 100644
--- a/tests/csaf_2_1/oasis.js
+++ b/tests/csaf_2_1/oasis.js
@@ -86,7 +86,6 @@ const skippedTests = new Set([
   'mandatory/oasis_csaf_tc-csaf_2_1-2024-6-1-01-03.json',
   'mandatory/oasis_csaf_tc-csaf_2_1-2024-6-1-03-01.json',
   'mandatory/oasis_csaf_tc-csaf_2_1-2024-6-1-03-02.json',
-  'mandatory/oasis_csaf_tc-csaf_2_1-2024-6-1-27-08-02.json',
   'mandatory/oasis_csaf_tc-csaf_2_1-2024-6-1-04-03.json',
   'recommended/oasis_csaf_tc-csaf_2_1-2024-6-2-38-13.json',
   'recommended/oasis_csaf_tc-csaf_2_1-2024-6-2-38-02.json',