CVE-2017-20189Public exploitNetwork attack vector

Remote code execution via serializable proxy gadget

Published Jan 22, 2024 · Updated Nov 3, 2025

Unsafe deserialization in Clojure before 1.9.0 allows remote attackers to execute arbitrary code through crafted serialized objects. Generated proxy classes implementing Serializable retain attacker-controlled Clojure function mappings, so ObjectInputStream.readObject() can trigger a hashCode chain that reaches clojure.main$eval_opt. Exploitation requires a server or other application to deserialize attacker-supplied Java objects; successful execution runs with the application's privileges.

CVSS severity9.8
Critical
EPSS probability1.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unsafe deserialization in Clojure before 1.9.0 allows remote attackers to execute arbitrary code through crafted serialized objects. Generated proxy classes implementing Serializable retain attacker-controlled Clojure function mappings, so ObjectInputStream.readObject() can trigger a hashCode chain that reaches clojure.main$eval_opt. Exploitation requires a server or other application to deserialize attacker-supplied Java objects; successful execution runs with the application's privileges.

The record

CVE
CVE-2017-20189
Published
Jan 22, 2024
Updated
Nov 3, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-502, T1059
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 22, 2024CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-502Deserialization of Untrusted Data
T1059Command and Scripting Interpreter

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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