# CVE-2020-9484: Potential remote code execution in Apache Tomcat

> Attackers can achieve remote code execution in Apache Tomcat by exploiting unsafe deserialization in the PersistenceManager when specific file control and configuration conditions are met.

- **Severity:** High 7.0 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 May 2020
- **Updated:** 8 Oct 2026
- **Also known as:** BIT-tomcat-2020-9484, DEBIAN-CVE-2020-9484, DLA-2217-1, GHSA-344f-f5vg-2jfj, MGASA-2020-0277, RHSA-2020:2483, RHSA-2020:2506, RHSA-2020:2529, RHSA-2020:2530, SUSE-SU-2020:1363-1, SUSE-SU-2020:1364-1, SUSE-SU-2020:1365-1, UBUNTU-CVE-2020-9484, openSUSE-SU-2020:0711-1

## What is CVE-2020-9484?

CVE-2020-9484 is a high-severity unsafe deserialization vulnerability in Apache Tomcat, published on 20 May 2020. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2020-9484?

17 open source packages ship an affected version, including org.apache.tomcat.embed:tomcat-embed-core, tomcat and org.apache.tomcat:tomcat-catalina. It affects 26 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.apache.tomcat.embed:tomcat-embed-core` | Maven | From 10.0.0-M1 | 10.0.0-M5 |
| `org.apache.tomcat.embed:tomcat-embed-core` | Maven | From 10.0.0-M1 | 10.0.0-M5 |
| `org.apache.tomcat.embed:tomcat-embed-core` | Maven | From 7.0.0 | 7.0.104 |
| `org.apache.tomcat.embed:tomcat-embed-core` | Maven | From 7.0.0 | 7.0.104 |
| `org.apache.tomcat.embed:tomcat-embed-core` | Maven | From 8.0.0 | 8.5.55 |
| `org.apache.tomcat.embed:tomcat-embed-core` | Maven | From 8.0.0 | 8.5.55 |
| `org.apache.tomcat.embed:tomcat-embed-core` | Maven | From 9.0.0 | 9.0.35 |
| `org.apache.tomcat.embed:tomcat-embed-core` | Maven | From 9.0.0 | 9.0.35 |
| `tomcat` | Bitnami | From 7.0.0 | 7.0.108, 8.5.63, 9.0.43 |
| `org.apache.tomcat:tomcat-catalina` | Maven | From 10.0.0-M1 | 10.0.0-M5 |
| `org.apache.tomcat:tomcat-catalina` | Maven | From 10.0.0-M1 | 10.0.0-M5 |
| `org.apache.tomcat:tomcat-catalina` | Maven | From 7.0.0 | 7.0.104 |
| `org.apache.tomcat:tomcat-catalina` | Maven | From 7.0.0 | 7.0.104 |
| `org.apache.tomcat:tomcat-catalina` | Maven | From 8.0.0 | 8.5.55 |
| `org.apache.tomcat:tomcat-catalina` | Maven | From 8.0.0 | 8.5.55 |
| `org.apache.tomcat:tomcat-catalina` | Maven | From 9.0.0 | 9.0.35 |
| `org.apache.tomcat:tomcat-catalina` | Maven | From 9.0.0 | 9.0.35 |
| `tomcat6` | Red Hat:enterprise_linux:6::client | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-admin-webapps` | Red Hat:enterprise_linux:6::client | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-docs-webapp` | Red Hat:enterprise_linux:6::client | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-el-2.1-api` | Red Hat:enterprise_linux:6::client | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-javadoc` | Red Hat:enterprise_linux:6::client | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-jsp-2.1-api` | Red Hat:enterprise_linux:6::client | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-lib` | Red Hat:enterprise_linux:6::client | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-servlet-2.5-api` | Red Hat:enterprise_linux:6::client | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-webapps` | Red Hat:enterprise_linux:6::client | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6` | Red Hat:enterprise_linux:6::computenode | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-admin-webapps` | Red Hat:enterprise_linux:6::computenode | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-docs-webapp` | Red Hat:enterprise_linux:6::computenode | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-el-2.1-api` | Red Hat:enterprise_linux:6::computenode | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-javadoc` | Red Hat:enterprise_linux:6::computenode | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-jsp-2.1-api` | Red Hat:enterprise_linux:6::computenode | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-lib` | Red Hat:enterprise_linux:6::computenode | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-servlet-2.5-api` | Red Hat:enterprise_linux:6::computenode | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-webapps` | Red Hat:enterprise_linux:6::computenode | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6` | Red Hat:enterprise_linux:6::server | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-admin-webapps` | Red Hat:enterprise_linux:6::server | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-docs-webapp` | Red Hat:enterprise_linux:6::server | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-el-2.1-api` | Red Hat:enterprise_linux:6::server | All versions | 0:6.0.24-115.el6_10 |
| `tomcat6-javadoc` | Red Hat:enterprise_linux:6::server | All versions | 0:6.0.24-115.el6_10 |

Products: Apache Tomcat, Canonical Ubuntu Linux, Debian Debian Linux, Fedoraproject Fedora, Mcafee Epolicy Orchestrator, Opensuse Leap, Oracle Agile Engineering Data Management, Oracle Agile Product Lifecycle Management, Oracle Communications Cloud Native Core Binding Support Function, Oracle Communications Cloud Native Core Policy, Oracle Communications Diameter Signaling Router, Oracle Communications Element Manager, Oracle Communications Instant Messaging Server, Oracle Communications Session Report Manager, Oracle Communications Session Route Manager, Oracle Database, Oracle Fmw Platform, Oracle Hospitality Guest Access, Oracle Instantis Enterprisetrack, Oracle Managed File Transfer and 6 more.

## How do I fix CVE-2020-9484?

Upgrade org.apache.tomcat.embed:tomcat-embed-core to a fixed version for your release line: 10.0.0-M5, 7.0.104, 8.5.55 or 9.0.35.

## Is CVE-2020-9484 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2020-9484 exists.

Public exploit code:

- tomcat使用了自带session同步功能时，不安全的配置（没有使用EncryptInterceptor）导致存在的反序列化漏洞，通过精心构造的数据包， 可以对使用了tomcat自带session同步功能的服务器进行攻击。PS:这个不是CVE-2020-9484，9484是session持久化的洞，这个是session集群同步的洞！ (github_poc): https://github.com/threedr3am/tomcat-cluster-session-sync-exp
- https://github.com/masahiro331/CVE-2020-9484 (github_poc): https://github.com/masahiro331/CVE-2020-9484
- 用Kali 2.0复现Apache Tomcat Session反序列化代码执行漏洞 (github_poc): https://github.com/IdealDreamLast/CVE-2020-9484
- https://github.com/PenTestical/CVE-2020-9484 (github_poc): https://github.com/PenTestical/CVE-2020-9484
- Remake of CVE-2020-9484 by Pentestical (github_poc): https://github.com/0dayCTF/CVE-2020-9484
- Exploit for Apache Tomcat deserialization (CVE-2020-9484) which could lead to RCE (github_poc): https://github.com/d3fudd/CVE-2020-9484_Exploit

## Other vulnerabilities in Apache Tomcat

- [CVE-2025-24813](https://insights.sbomify.com/CVE-2025-24813/): Apache Tomcat Path Equivalence (critical 10.0, exploited in the wild)
- [CVE-2016-8735](https://insights.sbomify.com/CVE-2016-8735/): Apache Tomcat Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2017-12617](https://insights.sbomify.com/CVE-2017-12617/): Apache Tomcat Remote Code Execution (high 8.1, exploited in the wild)
- [CVE-2017-12615](https://insights.sbomify.com/CVE-2017-12615/): Apache Tomcat on Windows Remote Code Execution (high 8.1, exploited in the wild)
- [CVE-2026-34486](https://insights.sbomify.com/CVE-2026-34486/): Apache Tomcat Missing Encryption of Sensitive Data (high 7.5, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-9484 and fix it if it is affected.

What it is: CVE-2020-9484 is a high-severity unsafe deserialization vulnerability in Apache Tomcat, published on 20 May 2020. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2020-9484 exists.

Affected packages and fixed versions:
- org.apache.tomcat.embed:tomcat-embed-core (Maven): affected from 10.0.0-M1; fixed in 10.0.0-M5
- org.apache.tomcat.embed:tomcat-embed-core (Maven): affected from 10.0.0-M1; fixed in 10.0.0-M5
- org.apache.tomcat.embed:tomcat-embed-core (Maven): affected from 7.0.0; fixed in 7.0.104
- org.apache.tomcat.embed:tomcat-embed-core (Maven): affected from 7.0.0; fixed in 7.0.104
- org.apache.tomcat.embed:tomcat-embed-core (Maven): affected from 8.0.0; fixed in 8.5.55
- org.apache.tomcat.embed:tomcat-embed-core (Maven): affected from 8.0.0; fixed in 8.5.55
- org.apache.tomcat.embed:tomcat-embed-core (Maven): affected from 9.0.0; fixed in 9.0.35
- org.apache.tomcat.embed:tomcat-embed-core (Maven): affected from 9.0.0; fixed in 9.0.35
- tomcat (Bitnami): affected from 7.0.0; fixed in 7.0.108, 8.5.63, 9.0.43
- org.apache.tomcat:tomcat-catalina (Maven): affected from 10.0.0-M1; fixed in 10.0.0-M5
- org.apache.tomcat:tomcat-catalina (Maven): affected from 10.0.0-M1; fixed in 10.0.0-M5
- org.apache.tomcat:tomcat-catalina (Maven): affected from 7.0.0; fixed in 7.0.104

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2020-9484/ (Markdown: https://insights.sbomify.com/CVE-2020-9484/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-9484
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-9484
- OSV: https://osv.dev/vulnerability/CVE-2020-9484

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-9484/
Summaries are generated and may contain mistakes; the official description above is the record.