Index: java/org/apache/catalina/loader/WebappClassLoaderBase.java
===================================================================
--- java/org/apache/catalina/loader/WebappClassLoaderBase.java	(revision 1729943)
+++ java/org/apache/catalina/loader/WebappClassLoaderBase.java	(working copy)
@@ -2763,12 +2763,12 @@
             return false;
 
         char ch;
-        if (name.startsWith("javax")) {
+        if (name.startsWith("javax") && name.length() > 5) {
             /* 5 == length("javax") */
             ch = name.charAt(5);
             if (isClassName && ch == '.') {
                 /* 6 == length("javax.") */
-                if (name.startsWith("servlet.jsp.jstl.", 6)) {
+                if (name.startsWith("servlet.jsp.jstl", 6)) {
                     return false;
                 }
                 if (name.startsWith("el.", 6) ||
@@ -2779,7 +2779,7 @@
                 }
             } else if (!isClassName && ch == '/') {
                 /* 6 == length("javax/") */
-                if (name.startsWith("servlet/jsp/jstl/", 6)) {
+                if (name.startsWith("servlet/jsp/jstl", 6)) {
                     return false;
                 }
                 if (name.startsWith("el/", 6) ||
@@ -2789,7 +2789,7 @@
                     return true;
                 }
             }
-        } else if (name.startsWith("org")) {
+        } else if (name.startsWith("org") && name.length() > 3) {
             /* 3 == length("org") */
             ch = name.charAt(3);
             if (isClassName && ch == '.') {
@@ -2796,7 +2796,7 @@
                 /* 4 == length("org.") */
                 if (name.startsWith("apache.", 4)) {
                     /* 11 == length("org.apache.") */
-                    if (name.startsWith("tomcat.jdbc.", 11)) {
+                    if (name.startsWith("tomcat.jdbc", 11)) {
                         return false;
                     }
                     if (name.startsWith("el.", 11) ||
@@ -2813,7 +2813,7 @@
                 /* 4 == length("org/") */
                 if (name.startsWith("apache/", 4)) {
                     /* 11 == length("org/apache/") */
-                    if (name.startsWith("tomcat/jdbc/", 11)) {
+                    if (name.startsWith("tomcat/jdbc", 11)) {
                         return false;
                     }
                     if (name.startsWith("el/", 11) ||
Index: test/org/apache/catalina/loader/TestWebappClassLoader.java
===================================================================
--- test/org/apache/catalina/loader/TestWebappClassLoader.java	(revision 1729943)
+++ test/org/apache/catalina/loader/TestWebappClassLoader.java	(working copy)
@@ -65,10 +65,11 @@
     public void testFilter() throws IOException {
 
         String[] classSuffixes = new String[]{
-            "some.package.Example"
+            "","some.package.Example"
         };
 
         String[] resourceSuffixes = new String[]{
+            "",
             "some/path/test.properties",
             "some/path/test"
         };
@@ -83,7 +84,7 @@
             "org.apache",
             "org.apache.tomcat.jdbc",
             "javax",
-            "javax.jsp.jstl",
+            "javax.servlet.jsp.jstl",
             "com.mycorp"
         };
 
@@ -106,30 +107,38 @@
 
             for (String prefix : prefixesPermit) {
                 for (String suffix : classSuffixes) {
-                    name = prefix + "." + suffix;
-                    Assert.assertTrue("Class '" + name + "' failed permit filter",
-                               !loader.filter(name, true));
                     if (prefix.equals("")) {
                         name = suffix;
-                        Assert.assertTrue("Class '" + name + "' failed permit filter",
-                                   !loader.filter(name, true));
+                    } else if (suffix.equals("")) {
+                        name = prefix;
+                    } else {
+                        name = prefix + "." + suffix;
                     }
+                    Assert.assertTrue("Class '" + name + "' failed permit filter",
+                               !loader.filter(name, true));
                 }
                 prefix = prefix.replace('.', '/');
                 for (String suffix : resourceSuffixes) {
-                    name = prefix + "/" + suffix;
-                    Assert.assertTrue("Resource '" + name + "' failed permit filter",
-                               !loader.filter(name, false));
                     if (prefix.equals("")) {
                         name = suffix;
-                        Assert.assertTrue("Resource '" + name + "' failed permit filter",
-                                   !loader.filter(name, false));
+                    } else if (suffix.equals("")) {
+                        name = prefix;
+                    } else {
+                        name = prefix + "/" + suffix;
                     }
+                    Assert.assertTrue("Resource '" + name + "' failed permit filter",
+                               !loader.filter(name, false));
                 }
             }
 
             for (String prefix : prefixesDeny) {
                 for (String suffix : classSuffixes) {
+                    if (suffix.equals("")) {
+                        name = prefix;
+                        Assert.assertTrue("Class '" + name + "' failed permit filter",
+                                !loader.filter(name, true));
+                        continue;
+                    }
                     if (prefix.equals("")) {
                         name = suffix;
                     } else {
@@ -140,6 +149,12 @@
                 }
                 prefix = prefix.replace('.', '/');
                 for (String suffix : resourceSuffixes) {
+                    if (suffix.equals("")) {
+                        name = prefix;
+                        Assert.assertTrue("Resource '" + name + "' failed permit filter",
+                                !loader.filter(name, false));
+                        continue;
+                    }
                     if (prefix.equals("")) {
                         name = suffix;
                     } else {