GHSA-j9h8-phrw-h4fh
HIGHGHSA-j9h8-phrw-h4fh is a high-severity (CVSS 8.5) Code Injection vulnerability in com.thoughtworks.xstream:xstream. 6 public exploit references exist, so weaponization risk is real. O3 Security confirms whether GHSA-j9h8-phrw-h4fh is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
XStream is vulnerable to a Remote Command Execution attack
Exploitation Status
Actively exploited in the wild
- CISA’s SSVC triage classifies this CVE as under active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for GHSA-j9h8-phrw-h4fh.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-j9h8-phrw-h4fh plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE sits: patch-first territory.
Where this sits among everything scored
Of 369,023 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
com.thoughtworks.xstream:xstreamReal-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 has sufficient rights to execute commands of the 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
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-2021-39144.
Credits
Ceclin and YXXX from the Tencent Security Response Center 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:
- Open an issue in XStream
- Email us at XStream Google Group
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | com.thoughtworks.xstream:xstream | all versions | 1.4.18 |
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. …
XStream is a simple library to serialize objects to XML and back again. …
XStream is a simple library to serialize objects to XML and back again. …
XStream is a simple library to serialize objects to XML and back again. …
XStream is a simple library to serialize objects to XML and back again. …
XStream is a simple library to serialize objects to XML and back again. …
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for com.thoughtworks.xstream:xstream. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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-j9h8-phrw-h4fh is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-j9h8-phrw-h4fh is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-j9h8-phrw-h4fh. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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.
Users who follow the recommended security framework with a whitelist to limit the types to the minimum required should not be affected. XStream 1.4.18 no longer uses a blacklist by default since it cannot be secured for general purposes. OpenShift Container Platform (OCP) delivers Jenkins LTS package with bundled…
Frequently Asked Questions
Is GHSA-j9h8-phrw-h4fh in your dependencies?
O3 detects GHSA-j9h8-phrw-h4fh across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.