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MEDIUM severity

XStream is vulnerable to an Arbitrary Code Execution attackGHSA-4hrm-m67v-5cxr

MEDIUM

GHSA-4hrm-m67v-5cxr is a medium-severity (CVSS 6.1) Unrestricted File Upload vulnerability in com.thoughtworks.xstream:xstream. 1 public exploit reference exists, so weaponization risk is real. A fix is available for com.thoughtworks.xstream:xstream — see the affected versions and patch details below.

Also known asBIT-activemq-2021-21346CVE-2021-21346
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
76.4%probability of exploitation in next 30 days
Very High Risk0.00%
Lower risk than most CVEs100th percentile — riskier than 100% of all scored CVEsHighest risk
0.00%32.7%65.5%98.2%3.7%76.4%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-4hrm-m67v-5cxr by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the 50–90% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
☕com.thoughtworks.xstream:xstream

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

Impact

The vulnerability may allow a remote attacker to load and execute arbitrary code from a remote host only by manipulating the processed input stream. No user is affected, who followed the recommendation to setup XStream's security framework with a whitelist limited to the minimal required types.

Patches

If you rely on XStream's default blacklist of the Security Framework, you will have to use at least version 1.4.16.

Workarounds

See workarounds for the different versions covering all CVEs.

References

See full information about the nature of the vulnerability and the steps to reproduce it in XStream's documentation for CVE-2021-21346.

Credits

wh1t3p1g G5-RD6@IIE found and reported the issue to XStream and provided the required information to reproduce it.

For more information

If you have any questions or comments about this advisory:

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
☕Mavencom.thoughtworks.xstream:xstreamall versions1.4.16com.thoughtworks.xstream:xstream:1.4.16

Affected Products

16 products · 41 configurations
Application
activemqapache
< 5.15.14
2 versions
5.16.05.16.1
Application
jmeterapache
< 5.5
range
OS
debian linuxdebian
3 versions
9.010.011.0
OS
fedorafedoraproject
3 versions
333435
Application
oncommand insightnetapp
all
Application
banking enterprise default managementoracle
2 versions
2.10.02.12.0
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.

XStream is a Java library to serialize objects to XML and back again. In…

x-stream.github.ioNVDJul 2021

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    Update com.thoughtworks.xstream:xstream to 1.4.16 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4hrm-m67v-5cxr is resolved across your whole dependency graph.

  3. Workarounds

    Treat uploaded files as untrusted until proven otherwise: validate the actual content type rather than the supplied extension, store uploads outside the web root on a volume mounted without execute permission, and rename them to server-generated identifiers so an attacker cannot choose the path a request will later resolve.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

OpenShift Container Platform (OCP) delivers Jenkins LTS package with bundled XStream library. Due to JEP-200 [1] and JEP-228 [2] Jenkins projects, OCP Jenkins package is not affected by this flaw. [1] https://github.com/jenkinsci/jep/blob/master/jep/200/README.adoc [2]…

ProductFixed inAdvisory
Red Hat Data Grid 8.2.0xstreamRHSA-2021:2139
Red Hat Enterprise Linux 7xstream-0:1.3.1-13.el7_9RHSA-2021:1354
Red Hat Fuse 7.10xstreamRHSA-2021:5134
Red Hat Integrationsee advisoryRHSA-2021:4918
Red Hat Integration Camel Quarkus 2see advisoryRHSA-2021:4767
RHDM 7.11.0xstreamRHSA-2021:2476
RHPAM 7.11.0xstreamRHSA-2021:2475

Frequently Asked Questions

### Impact The vulnerability may allow a remote attacker to load and execute arbitrary code from a remote host only by manipulating the processed input stream. No user is affected, who followed the recommendation to setup XStream's security framework with a whitelist limited to the minimal required types. ### Patches If you rely on XStream's default blacklist of the [Security Framework](https://x-stream.github.io/security.html#framework), you will have to use at least version 1.4.16. ### Workarounds See [workarounds](https://x-stream.github.io/security.html#workaround) for the different vers
O3 Security · Impact-Aware SCA

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XStream is vulnerable to an Arbitrary Code Execution attack