CVE-2022-27772
Temporary Directory Hijacking to Local Privilege Escalation Vulnerability in org.springframework.boot:spring-boot
Description
spring-boot versions prior to version `v2.2.11.RELEASE` was vulnerable to temporary directory hijacking. This vulnerability impacted the `org.springframework.boot.web.server.AbstractConfigurableWebServerFactory.createTempDir` method. The vulnerable method is used to create a work directory for embedded web servers such as Tomcat and Jetty. The directory contains configuration files, JSP/class files, etc. If a local attacker got the permission to write in this directory, they could completely take over the application (ie. local privilege escalation). #### Impact Location This vulnerability impacted the following source location: ```java /** * Return the absolute temp dir for given web server. * @param prefix server name * @return the temp dir for given server. */ protected final File createTempDir(String prefix) { try { File tempDir = File.createTempFile(prefix + ".", "." + getPort()); tempDir.delete(); tempDir.mkdir(); tempDir.deleteOnExit(); return tempDir; } ``` \- https://github.com/spring-projects/spring-boot/blob/ce70e7d768977242a8ea6f93188388f273be5851/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/server/AbstractConfigurableWebServerFactory.java#L165-L177 This vulnerability exists because `File.mkdir` returns `false` when it fails to create a directory, it does not throw an exception. As such, the following race condition exists: ```java File tmpDir =File.createTempFile(prefix + ".", "." + getPort()); // Attacker knows the full path of the file that will be generated // delete the file that was created tmpDir.delete(); // Attacker sees file is deleted and begins a race to create their own directory before Jetty. // and make a directory of the same name // SECURITY VULNERABILITY: Race Condition! - Attacker beats java code and now owns this directory tmpDir.mkdirs(); // This method returns 'false' because it was unable to create the directory. No exception is thrown. // Attacker can write any new files to this directory that they wish. // Attacker can read any files created by this process. ``` ### Prerequisites This vulnerability impacts Unix-like systems, and very old versions of Mac OSX and Windows as they all share the system temporary directory between all users. ### Patches This vulnerability was inadvertently fixed as a part of this patch: https://github.com/spring-projects/spring-boot/commit/667ccdae84822072f9ea1a27ed5c77964c71002d This vulnerability is patched in versions `v2.2.11.RELEASE` or later. ### Workarounds Setting the `java.io.tmpdir` system environment variable to a directory that is exclusively owned by the executing user will fix this vulnerability for all operating systems.