---
title: "CVE-2017-20189: Clojure classes can be used to craft a serialized object that runs arbitrary code on deserialization"
url: https://erroneo.us/security/cve/CVE-2017-20189/
description: "CVE-2017-20189 (org.clojure:clojure (Maven)): In Clojure before 1.9.0, classes can be used to construct a serialized object that executes arbitrary code…"
type: vulnerability-record
section: "Security Digest"
date_published: 2024-01-22
date_modified: 2025-11-04
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2017-20189"
kev: false
cvss: 9.8
epss: 0.01332
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2017-20189: Clojure classes can be used to craft a serialized object that runs arbitrary code on deserialization

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 1.3% , percentile 71: FIRST’s model estimates a 1.3% chance of exploitation activity in the next 30 days, higher than 71% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes org.clojure:clojure (Maven) < 1.9.0, fixed in 1.9.0 . Check your lockfile, including transitive dependencies.

## What it is

In Clojure before 1.9.0, classes can be used to construct a serialized object that executes arbitrary code upon deserialization. This is relevant if a server deserializes untrusted objects.

## Affected packages

- Maven `org.clojure:clojure` < 1.9.0 → fixed: 1.9.0

## Affected products (CVE record)

- n/a n/a: see advisory

## Severity

- CISA-ADP CVSS 3.1: 9.8 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`
- GitHub CVSS 3.1: 9.8 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 1.33% probability of exploitation activity in the next 30 days; percentile 71.

## Sources

- [GitHub Advisory GHSA-jgxc-8mwq-9xqw](https://github.com/advisories/GHSA-jgxc-8mwq-9xqw)
- [CVE.org record CVE-2017-20189](https://www.cve.org/CVERecord?id=CVE-2017-20189)
- [NVD entry CVE-2017-20189](https://nvd.nist.gov/vuln/detail/CVE-2017-20189)
- [hackmd.io](https://hackmd.io/%40fe1w0/HyefvRQKp)
- [clojure.atlassian.net](https://clojure.atlassian.net/browse/CLJ-2204)
- [github.com](https://github.com/frohoff/ysoserial/pull/68/files)
- [github.com](https://github.com/clojure/clojure/commit/271674c9b484d798484d134a5ac40a6df15d3ac3)
- [security.snyk.io](https://security.snyk.io/vuln/SNYK-JAVA-ORGCLOJURE-5740378)
- [security.netapp.com](https://security.netapp.com/advisory/ntap-20241108-0002/)
- [groups.google.com](https://groups.google.com/d/msg/clojure/WaL3hHzsevI/7zHU-L7LBQAJ)

---
Source page: https://erroneo.us/security/cve/CVE-2017-20189/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt