diff --git a/lib/github_advisory_sync.rb b/lib/github_advisory_sync.rb
index 04af518a98..817ce1300d 100644
--- a/lib/github_advisory_sync.rb
+++ b/lib/github_advisory_sync.rb
@@ -366,17 +366,145 @@ def patched_versions_for(package)
       return patched_versions
     end
 
+    def first_unaffected_versions_for(package)
+      first_unaffected_versions = []
+
+      vulnerabilities.each do |v|
+        if v['package']['name'] == package.name &&
+           v['vulnerableVersionRange']
+          first_unaffected_versions << v['vulnerableVersionRange']
+        end
+      end
+
+      first_unaffected_versions.sort
+    end
+
+    def set_fpv_vars(first_patched_versions)
+      if first_patched_versions.count > 0
+        if first_patched_versions.count == 1
+          fpv_operator = first_patched_versions.last[0,1]
+          fpv_value    = first_patched_versions.last[3..first_patched_versions.last.length]
+          #puts "FPV=#{first_patched_versions}; COUNT=[#{first_patched_versions.length}]"
+          #puts "FPV[1]=[#{fpv_operator}]; FPV[2]=[#{fpv_value}]"
+        else # > 1
+          puts "TODO: #Use Case 4: Multiple patched_verions ranges: TBD"
+          fpv_operator = "MULTIPLE"
+          fpv_value    = "MULTIPLE"
+        end
+      else # == 0
+        #fpv_operator = "EMPTY"
+        #fpv_value    = "EMPTY"
+      end
+
+      return fpv_operator, fpv_value
+    end
+
+    def unaffected_versions_for(package)
+      # The unaffected_versions field is similarly not directly available.
+      # This optional field must be inferred from the vulnerableVersionRange.
+      #
+      # EXAMPLE YAML OUTPUT:
+      #vulnerabilities:
+      #- package:
+      #    name: redcloth
+      #    ecosystem: RUBYGEMS
+      #  vulnerableVersionRange: "< 4.3.0"
+      #  firstPatchedVersion:
+      #    identifier: 4.3.0
+
+      # Need this code to compare vulnerableVersionRange and firstPatchedVersion[identifier]
+      first_patched_versions  = patched_versions_for(package)
+
+      fpv_operator, fpv_value = set_fpv_vars(first_patched_versions)
+
+      first_unaffected_versions = first_unaffected_versions_for(package)
+      unaffected_versions       = []
+
+      if !first_unaffected_versions.empty?
+        unaff_vers_range =
+          first_unaffected_versions.last[2..first_unaffected_versions.last.length]
+
+        case first_unaffected_versions.last[0,1]
+        when "<"
+          if first_unaffected_versions.last[0,2] == "<="
+            #Use Case 3: Example: TBD
+            #    vulnerableVersionRange: "<= 1.3.1"
+            #    firstPatchedVersion:
+            #      identifier: 1.4.0
+            #THEREFORE: unaffected_versions: "> 1.3.1, < 4.1.0"
+            unaff_vers_range =
+              first_unaffected_versions.last[3..first_unaffected_versions.last.length]
+            puts "uv3: [<=]: > #{unaff_vers_range}, < #{fpv_value}"
+            unaffected_versions << "> #{unaff_vers_range}, < #{fpv_value}"
+          else
+            if unaff_vers_range == fpv_value
+              #Use Case 1: gems/nokogiri/GHSA-fq42-c5rg-92c2.yml
+              #   vulnerableVersionRange: "< 1.13.2"
+              #    firstPatchedVersion:
+              #      identifier: 1.13.2
+              # THEREFORE: Do nothing.
+              puts "uc1A: [< && fvr == fpv_value], so do nothing"
+            else # < && !=
+              puts "uc1B: [< && fvr != fpv_value], so UNKNOWN"
+            end
+          end
+        when "="
+          if unaff_vers_range < fpv_value
+            #Use Case 2: Example: gems/spree_auth_devise/GHSA-8xfaw-5q82-3652.yml
+            #    vulnerableVersionRange:"= 4.1.0"
+            #    firstPatchedVersion:
+            #      identifier: 4.1.1
+            #THEREFORE: unaffected_versions: "< 4.1.0"
+            puts "uc4A: [=, uvr < fpv_v]: < #{unaff_vers_range}"
+            unaffected_versions << "< #{unaff_vers_range}"
+          else # = & !=
+            puts "uc4B: [=, uvr >= fpv_v]: UNKNOWN"
+            unaffected_verions << "[=, uvr >= fpv_v]: UNKNOWN"
+          end
+        when ">"
+          if first_unaffected_versions.last[0,2] == ">="
+            unaff_vers_range =
+              first_unaffected_versions.last[4..first_unaffected_versions.last.length]
+            puts "[>=]: #{unaff_vers_range}"
+            unaffected_versions << "[>=]: #{unaff_vers_range}"
+          else
+            puts "[>, !>=]: #{unaff_vers_range}"
+            unaffected_versions << "[>, !>=]: #{unaff_vers_range}"
+          end
+        when "!"
+          puts "[!]: #{unaff_vers_range}"
+          unaffected_versions << "[! OPERATOR]: #{unaff_vers_range}"
+        when "~"
+          puts "[~]: #{unaff_vers_range}"
+          unaffected_versions << "[~ OPERATOR]: #{unaff_vers_range}"
+        else
+          puts "[UNK OPERATOR]: #{unaff_vers_range}"
+          unaffected_versions << "[UNK OPERATOR]: #{unaff_vers_range}"
+        end
+      end
+
+      return unaffected_versions
+    end
+
     def create(package)
       filename_to_write = package.filename
 
       new_data = package.merge_data(
         "cvss_v3"             => ("<FILL IN IF AVAILABLE>" unless cvss),
-        "cvss_v4"             => "<FILL IN IF AVAILABLE>",
-        "unaffected_versions" => ["<OPTIONAL: FILL IN SEE BELOW>"]
+        "cvss_v4"             => "<FILL IN IF AVAILABLE>"
       )
 
+      unaffected_versions = unaffected_versions_for(package)
+
       patched_versions = patched_versions_for(package)
 
+      if !unaffected_versions.empty?
+        new_data['unaffected_versions'] = unaffected_versions if !patched_versions.empty?
+      else
+        # NOTE: Do not add "unaffected_versions:" field if empty.
+        puts "DEBUG: unaffected_versions: All Affected"
+      end
+
       if !patched_versions.empty?
         new_data['patched_versions'] = patched_versions
       else