# CVE-2020-9484

When using Apache Tomcat versions 10.0.0-M1 to 10.0.0-M4, 9.0.0.M1 to 9.0.34, 8.5.0 to 8.5.54 and 7.0.0 to 7.0.103 if a) an attacker is able to control the contents and name of a file on the server; and b) the server is configured to use the PersistenceManager with a FileStore; and c) the PersistenceManager is configured with sessionAttributeValueClassNameFilter=“null” (the default unless a SecurityManager is used) or a sufficiently lax filter to allow the attacker provided object to be deserialized; and d) the attacker knows the relative file path from the storage location used by FileStore to the file the attacker has control over; then, using a specifically crafted request, the attacker will be able to trigger remote code execution via deserialization of the file under their control. Note that all of conditions a) to d) must be true for the attack to succeed.

### 攻击条件#

• 存在文件上传(文件后缀为.session)

• 启用了tomcatsession持久化功能，在conf/context.xml中开启

• tomcat/libWEB-INF/lib下存在能够利用的反序列化gadget

### 漏洞原理#

org.apache.catalina.session.FileStore在使用load函数读取.session文件时，file函数未对/../路径穿越进行过滤

file函数存在路径穿越，因此在请求时可以构造JSESSIONID使得它可以读到任意位置的.session文件进行反序列化

### POC验证#

• STEP1: 配置context.xml文件，允许session持久化

• STEP2: 生成payload

• STEP3:将poc.session放入某路径下(path)

• STEP4:curl触发