CVE-2023-24815 (published 2023-02-09T18:15Z)

Vert.x-Web is a set of building blocks for building web applications in the java programming language. When running vertx web applications that serve files using `StaticHandler` on Windows Operating Systems and Windows File Systems, if the mount point is a wildcard (`*`) then an attacker can exfiltrate any class path resource. When computing the relative path to locate the resource, in case of wildcards, the code: `return "/" + rest;` from `Utils.java` returns the user input (without validation) as the segment to lookup. Even though checks are performed to avoid escaping the sandbox, given that the input was not sanitized `\\` are not properly handled and an attacker can build a path that is valid within the classpath. This issue only affects users deploying in windows environments and upgrading is the advised remediation path. There are no known workarounds for this vulnerability.

CVSS v3 base score: 5.3, MEDIUM (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N)

Weakness information:
cwe_id: CWE-22
cwe_name: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
description: The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
extended_description: 
            Many file operations are intended to take place within a restricted directory. By using special elements such as ".." and "/" separators, attackers can escape outside of the restricted location to access files or directories that are elsewhere on the system. One of the most common special elements is the "../" sequence, which in most modern operating systems is interpreted as the parent directory of the current location. This is referred to as relative path traversal. Path traversal also covers the use of absolute pathnames such as "/usr/local/bin" to access unexpected files. This is referred to as absolute path traversal.
         
         

Fix information:
repo_url: https://github.com/vert-x3/vertx-web
commit_details: repo_url: https://github.com/vert-x3/vertx-web
author: Paulo Lopes
author_date: 2023-02-02 14:08:19+01:00
msg: Fix the webroot escape to classpath on windows

Signed-off-by: Paulo Lopes <pmlopes@gmail.com>
repository: repo_url: https://github.com/vert-x3/vertx-web
repo_name: vert-x3/vertx-web
description: HTTP web applications for Vert.x
repo_language: Java
owner: vert-x3
file_changes: filename: Utils.java
change_type: ModificationType.MODIFY
diff: @@ -20,6 +20,7 @@ import io.vertx.core.MultiMap;
 import io.vertx.core.http.HttpHeaders;
 import io.vertx.core.http.HttpServerRequest;
 import io.vertx.core.http.HttpServerResponse;
+import io.vertx.core.http.impl.HttpUtils;
 import io.vertx.ext.web.Route;
 import io.vertx.ext.web.RoutingContext;
 
@@ -73,10 +74,12 @@ public class Utils {
     }
 
     if (!route.isExactPath()) {
-      final String rest = context.pathParam("*");
+      String rest = context.pathParam("*");
       if (rest != null) {
         // normalize
         if (rest.length() > 0) {
+          // remove any attempt to escape the web root and use UNIX style path separators
+          rest = HttpUtils.removeDots(rest.replace('\\', '/'));
           if (rest.charAt(0) == '/') {
             return rest;
           } else {

programming_language: Java
filename: StaticHandlerWindowsTest.java
change_type: ModificationType.ADD
diff: @@ -0,0 +1,57 @@
+/*
+ * Copyright 2014 Red Hat, Inc.
+ *
+ *  All rights reserved. This program and the accompanying materials
+ *  are made available under the terms of the Eclipse Public License v1.0
+ *  and Apache License v2.0 which accompanies this distribution.
+ *
+ *  The Eclipse Public License is available at
+ *  http://www.eclipse.org/legal/epl-v10.html
+ *
+ *  The Apache License v2.0 is available at
+ *  http://www.opensource.org/licenses/apache2.0.php
+ *
+ *  You may elect to redistribute this code under either of these licenses.
+ */
+
+package io.vertx.ext.web.handler;
+
+import io.vertx.core.http.HttpMethod;
+import io.vertx.ext.web.WebTestBase;
+import org.junit.Test;
+
+public class StaticHandlerWindowsTest extends WebTestBase {
+
+  @Test
+  public void testEscapeToClasspathFromWildcard() throws Exception {
+    router.clear();
+    router.route("/*").handler(StaticHandler.create("www"));
+    // attempt to escape to classpath, given that the handler is mounted on a wildcard,
+    // reading the wildcard must return a sanitized path and therefore not allow to escape.
+    testRequest(HttpMethod.GET, "/..\\.htdigest", 404, "Not Found");
+  }
+
+  @Test
+  public void testEscapeToClasspathFromNull() throws Exception {
+    router.clear();
+    router.route().handler(StaticHandler.create("www"));
+    // attempt to escape to classpath, given that the handler is mounted on a catch all path
+    testRequest(HttpMethod.GET, "/..\\.htdigest", 404, "Not Found");
+  }
+
+  @Test
+  public void testEscapeToClasspathFromRegEx() throws Exception {
+    router.clear();
+    router.routeWithRegex(".*").handler(StaticHandler.create("www"));
+    // attempt to escape to classpath, given that the handler is mounted on a regex,
+    testRequest(HttpMethod.GET, "/..\\.htdigest", 404, "Not Found");
+  }
+
+  @Test
+  public void testEscapeToClasspathFromFixedPath() throws Exception {
+    router.clear();
+    router.routeWithRegex("/").handler(StaticHandler.create("www"));
+    // attempt to escape to classpath, given that the handler is mounted on a regex,
+    testRequest(HttpMethod.GET, "/..\\.htdigest", 404, "Not Found");
+  }
+}

programming_language: Java