How severe is GHSA-hrcp-8f3q-4w2c?

GHSA-hrcp-8f3q-4w2c has a CVSS score of 5.4/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-hrcp-8f3q-4w2c?

GHSA-hrcp-8f3q-4w2c affects the following packages: com.thoughtworks.xstream:xstream (Maven). Ecosystems affected: Maven.

How do I fix GHSA-hrcp-8f3q-4w2c?

Update com.thoughtworks.xstream:xstream to version 1.4.16 or later. Run your dependency manager's update command and verify no transitive dependencies pin the vulnerable version. Use O3 Security's SCA scanner to confirm the fix is applied across your entire dependency tree.

Is GHSA-hrcp-8f3q-4w2c actively exploited in the wild?

Yes. There are 1 known exploit references for GHSA-hrcp-8f3q-4w2c, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for GHSA-hrcp-8f3q-4w2c?

GHSA-hrcp-8f3q-4w2c has an EPSS (Exploit Prediction Scoring System) score of 92.0%, placing it in the 100th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

What type of vulnerability is GHSA-hrcp-8f3q-4w2c?

GHSA-hrcp-8f3q-4w2c is classified as Unrestricted File Upload (CWE-434), Deserialization of Untrusted Data (CWE-502). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

Is there exploit tooling available for GHSA-hrcp-8f3q-4w2c?

A Nuclei detection template exists for GHSA-hrcp-8f3q-4w2c, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was GHSA-hrcp-8f3q-4w2c published, and has it been updated?

GHSA-hrcp-8f3q-4w2c was published on March 22, 2021 and was last updated on March 14, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕ Maven

GHSA-hrcp-8f3q-4w2c

MEDIUM

XStream is vulnerable to an Arbitrary Code Execution attack

Also known asBIT-activemq-2021-21351CVE-2021-21351

Published

Mar 22, 2021

Updated

Mar 14, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

1 known

EPSS Exploitation Probability

via FIRST.org ↗

92.0%probability of exploitation in next 30 days

Very High Risk100th percentile0.00%

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.

Blast Radius

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-2021-21351.

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:

Open an issue in XStream
Contact us at XStream Google Group

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`com.thoughtworks.xstream:xstream`	all versions	1.4.16

Exploits & PoCs

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

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

Is GHSA-hrcp-8f3q-4w2c in your stack?

O3 detects GHSA-hrcp-8f3q-4w2c across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my stack How O3 SCA works

CVSS Score

5.4/10

CVSS v3 base score

Vector breakdown

AV:Attack Vector

Network

AC:Attack Complexity

High

PR:Privileges Required

High

UI:User Interaction