CVE-2020-9484

CVE-2020-9484 is a high-severity vulnerability in Apache Tomcat with a CVSS 3.x base score of 7.0. Its EPSS exploit-prediction score of 57% places it in the 99th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-502.

Key facts

Description

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.

Frequently asked questions

What is 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.
How severe is CVE-2020-9484?
CVE-2020-9484 has a CVSS 3.x base score of 7.0, rated high severity. It is exploitable over local access with high attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2020-9484 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 57% (99th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-9484?
CVE-2020-9484 primarily affects Apache Tomcat. In total, 75 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-9484?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2020-9484 published?
CVE-2020-9484 was published on 2020-05-20 and last updated on 2026-06-17.

References

Affected products (75)

More vulnerabilities in Apache Tomcat

All CVEs affecting Apache Tomcat →

Other CWE-502 (Deserialization of Untrusted Data) vulnerabilities

Browse all CWE-502 (Deserialization of Untrusted Data) vulnerabilities →