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☕ Maven
Not in CISA KEV
HIGH severity

CVE-2017-3203 — spring-flex

HIGH

CVE-2017-3203 is a high-severity (CVSS 8.1) Deserialization of Untrusted Data vulnerability in org.springframework.flex:spring-flex. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.

Deserialization of Untrusted Data in Spring-flex

Published
Updated
Affected
1 pkg
Patched
See advisory
Exploits
1 known
Exploitation data as of Oct 21, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
6.2%probability of exploitation in next 30 days
Lower Risk-0.08%
Lower risk than most CVEs94th percentile — riskier than 94% of all scored CVEsHighest risk
4.07%7.91%11.7%15.6%13.4%6.2%Apr 26Aug 26Oct 26

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

1 pkg affected
☕org.springframework.flex:spring-flex

Real-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

The Java implementations of AMF3 deserializers in Pivotal/Spring Spring-flex derive class instances from java.io.Externalizable rather than the AMF3 specification's recommendation of flash.utils.IExternalizable. A remote attacker with the ability to spoof or control an RMI server connection may be able to send serialized Java objects that execute arbitrary code when deserialized.

Affected Packages

1 total
EcosystemPackageVulnerable rangeFix
☕Mavenorg.springframework.flex:spring-flexall versionsNo fix

Affected Products

1 product · 1 configurations
Application
spring-flexpivotal
all
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

The Java implementations of AMF3 deserializers in Pivotal/Spring Spring-…

codewhitesec.blogspot.comNVDOct 2019

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.springframework.flex:spring-flex, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Remediation status

    The records we use list no patched version of org.springframework.flex:spring-flex for CVE-2017-3203. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.

  3. Mitigate without a patch

    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

The Java implementations of AMF3 deserializers in Pivotal/Spring Spring-flex derive class instances from java.io.Externalizable rather than the AMF3 specification's recommendation of flash.utils.IExternalizable. A remote attacker with the ability to spoof or control an RMI server connection may be able to send serialized Java objects that execute arbitrary code when deserialized.
O3 Security · Impact-Aware SCA

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CVE-2017-3203: spring-flex RCE (High 8.1)