How severe is CVE-2021-29505?

CVE-2021-29505 has a CVSS score of 8.8/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-29505?

CVE-2021-29505 affects the following packages: com.thoughtworks.xstream:xstream (Maven). Ecosystems affected: Maven.

How do I fix CVE-2021-29505?

Update com.thoughtworks.xstream:xstream to 1.4.17 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-29505 is resolved across your whole dependency graph.

How do I detect CVE-2021-29505 in my Maven dependencies?

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.

How do I mitigate CVE-2021-29505 if there is no patch (or I can't update yet)?

Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.

Is CVE-2021-29505 actively exploited in the wild?

Yes. There are 2 known exploit references for CVE-2021-29505, 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 CVE-2021-29505?

CVE-2021-29505 has an EPSS (Exploit Prediction Scoring System) score of 77.2%, 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 CVE-2021-29505?

CVE-2021-29505 is classified as Code Injection (CWE-94), 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 CVE-2021-29505?

A Nuclei detection template exists for CVE-2021-29505, 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 CVE-2021-29505 published, and has it been updated?

CVE-2021-29505 was published on May 28, 2021 and was last updated on October 9, 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

Not in CISA KEV

HIGH severity

CVE-2021-29505 — xstream

HIGHFix: x-stream/xstream@24fac82

CVE-2021-29505 is a high-severity (CVSS 8.8) Code Injection vulnerability in com.thoughtworks.xstream:xstream. 2 public exploit references exist, so weaponization risk is real. A fix is available for com.thoughtworks.xstream:xstream — see the affected versions and patch details below.

XStream is vulnerable to a Remote Command Execution attack

Also known asGHSA-7chv-rrw6-w6fc

Published

May 28, 2021

Updated

Oct 9, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

2 known

Exploitation data as of Oct 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

A successful exploit gives an attacker total control of the affected component, not partial access.
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 CVE-2021-29505.

EPSS Exploitation Probability

via FIRST.org ↗

77.2%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

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

How urgent is this, really

CVE-2021-29505 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).

Where this sits among everything scored

Of 385,987 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 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

If you rely on XStream's default blacklist of the Security Framework, you will have to use at least version 1.4.17.

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-2021-29505.

Credits

V3geB1rd, white hat hacker from 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

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`com.thoughtworks.xstream:xstream`	all versions	1.4.17`com.thoughtworks.xstream:xstream:1.4.17`

Affected Products

17 products · 42 configurations

debian linuxdebian

3 versions

9.010.011.0

fedorafedoraproject

3 versions

333435

Application

snapmanagernetapp

all

Application

banking cash managementoracle

3 versions

14.214.314.5

Application

banking corporate lending process managementoracle

3 versions

14.2.014.3.014.5.0

Application

banking credit facilities process managementoracle

3 versions

14.2.014.3.014.5.0

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 software for serializing Java objects to XML and back again. …

github.comGithubJun 2021

Detection & mitigation playbook

Open-source dependency

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.
Fix
Update com.thoughtworks.xstream:xstream to 1.4.17 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-29505 is resolved across your whole dependency graph.
Workarounds
Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.

How to detect CVE-2021-29505

A community-maintained Nuclei template exists for this CVE. You can scan for it directly:

nuclei -id cve-2021-29505 -u https://target

Template: XStream <1.4.17 - Remote Code Execution
Severity: high
Impact: Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code on the target system.
Remediation: Patched in 1.4.17.

Template by ProjectDiscovery nuclei-templates (pwnhxl), MIT licensed. View the full template. Scan only systems you are authorised to test.

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. CodeReady Studio 12 ships a version of xstream that is affected by this flaw as a transitive dependency for the Wise…

Workaround published by Red Hat

Depending on the version of XStream used there are various usage patterns that mitigate this flaw, though we would strongly recommend using the allow list approach if at all possible as there are likely more class combinations the deny list approach may not address. Allow list approach ```java XStream xstream = new XStream(); XStream.setupDefaultSecurity(xstream); xstream.allowTypesByWildcard(new String[] {"com.misc.classname"}) ``` Deny list for XStream 1.4.16 (this should also address some previous flaws found in 1.4.7 - > 1.4.15) ```java xstream.denyTypesByRegExp(new String[]{ ".*\\.Lazy(?:Search)?Enumeration.*", "(?:java|sun)\\.rmi\\..*" }); ``` Deny list for XStream…

Source: Red Hat security advisory for CVE-2021-29505 (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat Data Grid 8.3.0	`xstream`	RHSA-2022:0520
Red Hat Enterprise Linux 7	`xstream-0:1.3.1-14.el7_9`	RHSA-2021:2683
Red Hat Fuse 7.11	`xstream`	RHSA-2022:5532
Red Hat Integration	`xstream`	RHSA-2021:4918
Red Hat Integration Camel Quarkus 2	see advisory	RHSA-2021:4767
RHDM 7.12.0	`xstream`	RHSA-2022:0297
RHPAM 7.12.0	`xstream`	RHSA-2022:0296

Frequently Asked Questions

### 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 If you rely on XStream's default blacklist of the Security Framework, you will have to use at least version 1.4.17. ### Workarounds See [workarounds](https://x-stream.github.io/security.html#workaround) for the different versions covering all CVEs. ### References See full infor

O3 Security · Impact-Aware SCA

Is CVE-2021-29505 in your dependencies?

Find it across Maven, including transitive dependencies.

Scan my dependencies How O3 SCA works