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MEDIUM severity

XStream can cause a Denial of ServiceGHSA-6wf9-jmg9-vxcc

MEDIUM

GHSA-6wf9-jmg9-vxcc is a medium-severity (CVSS 6.5) Deserialization of Untrusted Data 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 asCVE-2021-39140
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Oct 12, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-6wf9-jmg9-vxcc.

EPSS Exploitation Probability

via FIRST.org ↗
5.9%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs93th percentile — riskier than 93% of all scored CVEsHighest risk
0.00%2.56%5.12%7.68%0.1%5.9%5.9%5.9%5.9%May 26Sep 26Oct 26

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

How urgent is this, really

GHSA-6wf9-jmg9-vxcc 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 < 10% 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 allocate 100% CPU time on the target system depending on CPU type or parallel execution of such a payload resulting in a denial of service 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

XStream 1.4.18 uses no longer a blacklist by default, since it cannot be secured for general purpose.

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-2021-39140.

Credits

The vulnerability was discovered and reported by Lai Han of nsfocus security team.

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 versions1.4.18com.thoughtworks.xstream:xstream:1.4.18

Affected Products

15 products · 36 configurations
OS
debian linuxdebian
3 versions
9.010.011.0
OS
fedorafedoraproject
3 versions
333435
Application
snapmanagernetapp
all
Application
business activity monitoringoracle
1 version
12.2.1.4.0
Application
commerce guided searchoracle
1 version
11.3.2
Application
communications billing and revenue management elastic charging engineoracle
2 versions
11.312.0
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 simple library to serialize objects to XML and back again. …

x-stream.github.ioNVDAug 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 1.4.18 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-6wf9-jmg9-vxcc is resolved across your whole dependency graph.

  3. 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.

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 HatModerate

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. This version of XStream library will be delivered in the future Jenkins releases. [1]…

ProductFixed inAdvisory
Red Hat Data Grid 8.3.0xstreamRHSA-2022:0520
Red Hat Enterprise Linux 7xstream-0:1.3.1-16.el7_9RHSA-2021:3956
Red Hat IntegrationxstreamRHSA-2021:4918
Red Hat Integration Camel Quarkus 2see advisoryRHSA-2021:4767
RHDM 7.12.0xstreamRHSA-2022:0297
RHPAM 7.12.0xstreamRHSA-2022:0296
UbuntuMEDIUM
USN-5946-1Ubuntu

Frequently Asked Questions

### Impact The vulnerability may allow a remote attacker to allocate 100% CPU time on the target system depending on CPU type or parallel execution of such a payload resulting in a denial of service 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 XStream 1.4.18 uses no longer a blacklist by default, since it cannot be secured for general purpose. ### Workarounds See [workarounds](https://x-stream.github.io/security.html#workaround) fo
O3 Security · Impact-Aware SCA

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XStream can cause a Denial of Service (Medium 6.5)