CVE-2017-20189 is a critical-severity (CVSS 9.8) Deserialization of Untrusted Data vulnerability in org.clojure:clojure. 2 public exploit or proof-of-concept references are indexed, so weaponization risk is real. A fix is available for org.clojure:clojure — see the affected versions and patch details below.
Clojure classes can be used to craft a serialized object that runs arbitrary code on deserialization
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2017-20189.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
org.clojure:clojureReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.clojure:clojure | all versions | 1.9.0org.clojure:clojure:1.9.0 |
Affected Products
clojureclojureResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.clojure:clojure, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.clojure:clojure to 1.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2017-20189 is resolved across your whole dependency graph.
Workarounds
Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.
Frequently Asked Questions
Is CVE-2017-20189 in your dependencies?
Find it across Maven, including transitive dependencies.