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+# Apache Shiro Authentication Bypass Vulnerability (CVE-2020-1957)
+
+[中文版本(Chinese version)](README.zh-cn.md)
+
+Apache Shiro is a powerful and easy-to-use Java security framework that performs authentication, authorization, cryptography, and session management.
+
+In versions of Apache Shiro prior to 1.5.2 with the Spring dynamic controller, an attacker can construct a maliciously crafted request using `..;` to bypass the directory authentication.
+
+Reference links:
+
+- <https://github.com/apache/shiro/commit/3708d7907016bf2fa12691dff6ff0def1249b8ce#diff-98f7bc5c0391389e56531f8b3754081aL139>
+- <https://xz.aliyun.com/t/8281>
+- <https://blog.spoock.com/2020/05/09/cve-2020-1957/>
+
+## Vulnerability environment
+
+Start an application with Spring 2.2.2 and Shiro 1.5.1 by executing the following command.
+
+```
+docker compose up -d
+```
+
+Once the environment is started, visit ``http://your-ip:8080`` to see the home page.
+
+The configuration of URL permissions in this application is as follows.
+
+``` java
+@Bean
+public ShiroFilterChainDefinition shiroFilterChainDefinition() {
+    DefaultShiroFilterChainDefinition chainDefinition = new DefaultShiroFilterChainDefinition();
+    chainDefinition.addPathDefinition("/login.html", "authc"); // need to accept POSTs from the login form
+    chainDefinition.addPathDefinition("/logout", "logout");
+    chainDefinition.addPathDefinition("/admin/**", "authc");
+    return chainDefinition;
+}
+```
+
+## Exploit
+
+A direct request to the admin page `/admin/` is inaccessible and will be redirected to the login page.
+
+![](1.png)
+
+Construct a malicious request `/xxx/..;/admin/` to bypass authentication checks and access the admin page.
+
+![](2.png)