diff -up ./java/org/apache/catalina/session/FileStore.java.orig ./java/org/apache/catalina/session/FileStore.java
--- ./java/org/apache/catalina/session/FileStore.java.orig	2020-05-21 16:11:53.278807740 -0400
+++ ./java/org/apache/catalina/session/FileStore.java	2020-05-21 16:13:55.102531264 -0400
@@ -32,6 +32,8 @@ import org.apache.catalina.Context;
 import org.apache.catalina.Loader;
 import org.apache.catalina.Session;
 import org.apache.juli.logging.Log;
+import org.apache.juli.logging.LogFactory;
+import org.apache.tomcat.util.res.StringManager;
 
 /**
  * Concrete implementation of the <b>Store</b> interface that utilizes
@@ -42,6 +44,10 @@ import org.apache.juli.logging.Log;
  */
 public final class FileStore extends StoreBase {
 
+    private static final Log log = LogFactory.getLog(FileStore.class);
+    private static final StringManager sm = StringManager.getManager(FileStore.class);
+
+
     // ----------------------------------------------------- Constants
 
     /**
@@ -389,11 +395,20 @@ public final class FileStore extends Sto
      *    used in the file naming.
      */
     private File file(String id) throws IOException {
-        if (this.directory == null) {
+        File storageDir = directory();
+        if (storageDir == null) {
             return null;
         }
+
         String filename = id + FILE_EXT;
-        File file = new File(directory(), filename);
+        File file = new File(storageDir, filename);
+
+        // Check the file is within the storage directory
+        if (!file.getCanonicalPath().startsWith(storageDir.getCanonicalPath())) {
+            log.warn(sm.getString("fileStore.invalid", file.getPath(), id));
+            return null;
+        }
+
         return file;
     }
 }
diff -up ./java/org/apache/catalina/session/LocalStrings.properties.orig ./java/org/apache/catalina/session/LocalStrings.properties
--- ./java/org/apache/catalina/session/LocalStrings.properties.orig	2020-05-21 16:14:03.128513044 -0400
+++ ./java/org/apache/catalina/session/LocalStrings.properties	2020-05-21 16:14:14.058488232 -0400
@@ -20,6 +20,7 @@ fileStore.loading=Loading Session {0} fr
 fileStore.removing=Removing Session {0} at file {1}
 fileStore.deleteFailed=Unable to delete file [{0}] which is preventing the creation of the session storage location
 fileStore.createFailed=Unable to create directory [{0}] for the storage of session data
+fileStore.invalid=Invalid persistence file [{0}] for session ID [{1}]
 JDBCStore.close=Exception closing database connection {0}
 JDBCStore.saving=Saving Session {0} to database {1}
 JDBCStore.loading=Loading Session {0} from database {1}
diff -up ./webapps/docs/changelog.xml.orig ./webapps/docs/changelog.xml
--- ./webapps/docs/changelog.xml.orig	2020-05-21 16:14:22.575468899 -0400
+++ ./webapps/docs/changelog.xml	2020-05-21 16:15:39.413294473 -0400
@@ -57,6 +57,15 @@
   They eventually become mixed with the numbered issues. (I.e., numbered
   issues do not "pop up" wrt. others).
 -->
+<section name="Tomcat 7.0.76-14 (csutherl)">
+  <subsection name="Catalina">
+    <changelog>
+      <add>
+        Improve validation of storage location when using FileStore. (markt)
+      </add>
+    </changelog>
+  </subsection>
+</section>
 <section name="Tomcat 7.0.76-12 (csutherl)">
   <subsection name="jdbc-pool">
     <changelog>