Index: apache-tomcat-9.0.36-src/java/org/apache/catalina/webresources/AbstractFileResourceSet.java
===================================================================
--- apache-tomcat-9.0.36-src.orig/java/org/apache/catalina/webresources/AbstractFileResourceSet.java
+++ apache-tomcat-9.0.36-src/java/org/apache/catalina/webresources/AbstractFileResourceSet.java
@@ -22,11 +22,15 @@ import java.net.MalformedURLException;
 import java.net.URL;
 
 import org.apache.catalina.LifecycleException;
+import org.apache.juli.logging.Log;
+import org.apache.juli.logging.LogFactory;
 import org.apache.tomcat.util.compat.JrePlatform;
 import org.apache.tomcat.util.http.RequestUtil;
 
 public abstract class AbstractFileResourceSet extends AbstractResourceSet {
 
+    private static final Log log = LogFactory.getLog(AbstractFileResourceSet.class);
+
     protected static final String[] EMPTY_STRING_ARRAY = new String[0];
 
     private File fileBase;
@@ -128,6 +132,19 @@ public abstract class AbstractFileResour
             canPath = normalize(canPath);
         }
         if (!canPath.equals(absPath)) {
+            if (!canPath.equalsIgnoreCase(absPath)) {
+                // Typically means symlinks are in use but being ignored. Given
+                // the symlink was likely created for a reason, log a warning
+                // that it was ignored.
+                String msg = sm.getString("abstractFileResourceSet.canonicalfileCheckFailed",
+                        getRoot().getContext().getName(), absPath, canPath);
+                // Log issues with configuration files at a higher level
+                if(absPath.startsWith("/META-INF/") || absPath.startsWith("/WEB-INF/")) {
+                    log.error(msg);
+                } else {
+                    log.warn(msg);
+                }
+            }
             return null;
         }
 
@@ -144,7 +161,7 @@ public abstract class AbstractFileResour
         // expression irrespective of input length.
         for (int i = 0; i < len; i++) {
             char c = name.charAt(i);
-            if (c == '\"' || c == '<' || c == '>') {
+            if (c == '\"' || c == '<' || c == '>' || c == ':') {
                 // These characters are disallowed in Windows file names and
                 // there are known problems for file names with these characters
                 // when using File#getCanonicalPath().
Index: apache-tomcat-9.0.36-src/java/org/apache/catalina/webresources/LocalStrings.properties
===================================================================
--- apache-tomcat-9.0.36-src.orig/java/org/apache/catalina/webresources/LocalStrings.properties
+++ apache-tomcat-9.0.36-src/java/org/apache/catalina/webresources/LocalStrings.properties
@@ -15,6 +15,8 @@
 
 abstractArchiveResourceSet.setReadOnlyFalse=Archive based WebResourceSets such as those based on JARs are hard-coded to be read-only and may not be configured to be read-write
 
+abstractFileResourceSet.canonicalfileCheckFailed=Resource for web application [{0}] at path [{1}] was not loaded as the canonical path [{2}] did not match. Use of symlinks is one possible cause.
+
 abstractResource.getContentFail=Unable to return [{0}] as a byte array
 abstractResource.getContentTooLarge=Unable to return [{0}] as a byte array since the resource is [{1}] bytes in size which is larger than the maximum size of a byte array
 
Index: apache-tomcat-9.0.36-src/webapps/docs/changelog.xml
===================================================================
--- apache-tomcat-9.0.36-src.orig/webapps/docs/changelog.xml
+++ apache-tomcat-9.0.36-src/webapps/docs/changelog.xml
@@ -81,6 +81,10 @@
         <bug>64493</bug>: Revert possible change of returned protocol
         attribute value on the <code>Connector</code>. (remm)
       </fix>
+      <add>
+        <bug>64871</bug>: Log a warning if Tomcat blocks access to a file
+        because it uses symlinks. (markt)
+      </add>
     </changelog>
   </subsection>
   <subsection name="Coyote">