Merge branch 'security-nuget-api-regex-dos' into 'master'

Update non-negative integer regex to protect against regex DoS

See merge request gitlab-org/security/gitlab!1127

changelogs/unreleased/security-nuget-regex-update-redos.yml

+---
+title: Update NuGet regular expression to protect against ReDoS
+merge_request:
+author:
+type: security

lib/api/concerns/packages/nuget_endpoints.rb

@@ -15,7 +15,7 @@ module API
         extend ActiveSupport::Concern
 
         POSITIVE_INTEGER_REGEX = %r{\A[1-9]\d*\z}.freeze
-        NON_NEGATIVE_INTEGER_REGEX = %r{\A0|[1-9]\d*\z}.freeze
+        NON_NEGATIVE_INTEGER_REGEX = %r{\A(0|[1-9]\d*)\z}.freeze
 
         included do
           helpers do