diff --git a/metadata/dependency_metadata.py b/metadata/dependency_metadata.py
index 40812be611..14e964240a 100644
--- a/metadata/dependency_metadata.py
+++ b/metadata/dependency_metadata.py
@@ -305,6 +305,10 @@ class DependencyMetadata:
     def name(self) -> Optional[str]:
         return self._return_as_property(known_fields.NAME)
 
+    @property
+    def mitigated(self) -> Optional[List[str]]:
+        return self._return_as_property(known_fields.MITIGATED)
+
     @property
     def short_name(self) -> Optional[str]:
         return self._return_as_property(known_fields.SHORT_NAME)
diff --git a/metadata/fields/custom/mitigated.py b/metadata/fields/custom/mitigated.py
new file mode 100644
index 0000000000..f44c5cf9d2
--- /dev/null
+++ b/metadata/fields/custom/mitigated.py
@@ -0,0 +1,85 @@
+#!/usr/bin/env python3
+# Copyright 2025 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import re
+from typing import List, Optional, Tuple
+
+import metadata.fields.field_types as field_types
+import metadata.fields.util as util
+import metadata.validation_result as vr
+
+# List of supported vulnerability ID prefixes.
+_VULN_PREFIXES = [
+    "CVE",  # Common Vulnerabilities and Exposures.
+    "GHSA",  # GitHub Security Advisory.
+    "PYSEC",  # Python Security Advisory.
+    "OSV",  # Open Source Vulnerability.
+    "DSA",  # Debian Security Advisory.
+]
+
+_PREFIX_PATTERN = "|".join(_VULN_PREFIXES)
+_VULN_ID_PATTERN = re.compile(
+    rf"^({_PREFIX_PATTERN})-[a-zA-Z0-9]{{4}}-[a-zA-Z0-9:-]+$")
+
+
+def validate_vuln_ids(vuln_ids: str) -> Tuple[List[str], List[str]]:
+    """
+    Validates a list of vulnerability identifiers and returns valid and invalid IDs.
+
+    Supports multiple formats:
+    - CVE IDs (e.g., CVE-2024-12345)
+    - GitHub Security Advisories (e.g., GHSA-1234-5678-90ab)
+    - Python Security Advisories (e.g., PYSEC-2024-1234)
+    - Open Source Vulnerabilities (e.g., OSV-2024-1234)
+    - Debian Security Advisories (e.g., DSA-1234-1)
+
+    Args:
+        vuln_ids: List of vulnerability identifiers to validate
+
+    Returns:
+        Tuple of (valid_ids, invalid_ids)
+    """
+    valid_vuln_ids = []
+    invalid_vuln_ids = []
+
+    for cve in vuln_ids.split(","):
+        cve_stripped = cve.strip()
+        if _VULN_ID_PATTERN.match(cve_stripped):
+            valid_vuln_ids.append(cve_stripped)
+        else:
+            invalid_vuln_ids.append(cve)
+
+    return valid_vuln_ids, invalid_vuln_ids
+
+
+class MitigatedField(field_types.SingleLineTextField):
+    """Field for comma-separated vulnerability IDs."""
+
+    def __init__(self):
+        super().__init__(name="Mitigated")
+
+    def validate(self, value: str) -> Optional[vr.ValidationResult]:
+        """Checks if the value contains valid CVE IDs."""
+        if util.is_empty(value):
+            return None
+        _, invalid_vuln_ids = validate_vuln_ids(value)
+
+        if invalid_vuln_ids:
+            return vr.ValidationWarning(
+                reason=f"{self._name} contains invalid vulnerability IDs.",
+                additional=[
+                    f"Invalid Vulnerability IDs: {util.quoted(invalid_vuln_ids)}",
+                    "The following identifiers are supported: " +
+                    ", ".join(_VULN_PREFIXES),
+                ],
+            )
+
+        return None
+
+    def narrow_type(self, value: str) -> Optional[List[str]]:
+        if not value:
+            return None
+        vuln_ids, _ = validate_vuln_ids(value)
+        return vuln_ids
diff --git a/metadata/fields/known.py b/metadata/fields/known.py
index 6f97fccfcc..a0a64916a5 100644
--- a/metadata/fields/known.py
+++ b/metadata/fields/known.py
@@ -19,6 +19,7 @@ import metadata.fields.custom.date
 import metadata.fields.custom.license
 import metadata.fields.custom.license_file
 import metadata.fields.custom.local_modifications
+import metadata.fields.custom.mitigated
 import metadata.fields.custom.url
 import metadata.fields.custom.version
 import metadata.fields.custom.revision
@@ -46,6 +47,7 @@ VERSION = metadata.fields.custom.version.VersionField()
 REVISION = metadata.fields.custom.revision.RevisionField()
 LOCAL_MODIFICATIONS = metadata.fields.custom.local_modifications.LocalModificationsField(
 )
+MITIGATED = metadata.fields.custom.mitigated.MitigatedField()
 
 ALL_FIELDS = (
     NAME,
@@ -61,6 +63,7 @@ ALL_FIELDS = (
     SHIPPED_IN_CHROMIUM,
     LICENSE_ANDROID_COMPATIBLE,
     CPE_PREFIX,
+    MITIGATED,
     DESCRIPTION,
     LOCAL_MODIFICATIONS,
 )
diff --git a/metadata/tests/fields_test.py b/metadata/tests/fields_test.py
index 30f449309a..188d162746 100644
--- a/metadata/tests/fields_test.py
+++ b/metadata/tests/fields_test.py
@@ -18,6 +18,7 @@ sys.path.insert(0, _ROOT_DIR)
 import metadata.fields.known as known_fields
 import metadata.fields.field_types as field_types
 import metadata.validation_result as vr
+import metadata.fields.custom.mitigated
 
 
 class FieldValidationTest(unittest.TestCase):
@@ -232,5 +233,32 @@ class FieldValidationTest(unittest.TestCase):
             self.assertFalse(
                 known_fields.LOCAL_MODIFICATIONS.should_terminate_field(value))
 
+    def test_vulnerability_ids(self):
+        valid_ids = [
+            "CVE-2024-12345",
+            "CVE-2024-1234567",
+            "PYSEC-2024-1234",
+            "OSV-2024-1234",
+            "DSA-1234-1",
+            "GHSA-1234-5678-90ab",
+        ]
+
+        invalid_ids = [
+            "CVE-123-456",
+            "GHSA-123-456",
+            "PYSEC-2024",  # Missing ID part.
+            "NOT-A-VALID-ID",  # Bad prefix.
+            "CVE_2024_12345",  # Wrong separator.
+            "",  # Empty.
+            " ",  # Just space.
+        ]
+
+        test_ids = valid_ids + invalid_ids
+        valid_result, invalid_result = metadata.fields.custom.mitigated.validate_vuln_ids(
+            ",".join(test_ids))
+
+        self.assertListEqual(sorted(valid_result), sorted(valid_ids))
+        self.assertListEqual(sorted(invalid_result), sorted(invalid_ids))
+
 if __name__ == "__main__":
     unittest.main()