Apache Tomcat Deserialization of Untrusted Data Vulnerability - 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 sessionAttributeValueClassNameFilterquotnullquot (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.