CVE-2020-9484
HighCVSS 7.0Exploitation Probability (EPSS)
Very high risk99th percentile - higher than 99% of all known CVEs
Summary
In 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 an attacker can control the contents and name of a file on the server, and the server is configured with PersistenceManager using FileStore and appropriate filters, remote code execution via deserialization is possible.
Risk Assessment
An attacker can execute arbitrary code on the server, leading to full system compromise.
Recommendation
Upgrade Apache Tomcat to a version that includes the fix (e.g., 9.0.35, 8.5.55, 7.0.104 or later) and configure PersistenceManager with appropriate filters.
Original NVD description (English source)
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.