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 version 1.4.17 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 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 90.3%, 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 April 16, 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

CVE-2021-29505

HIGH

XStream is vulnerable to a Remote Command Execution attack

Also known asGHSA-7chv-rrw6-w6fc

Published

May 28, 2021

Updated

Apr 16, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

2 known

EPSS Exploitation Probability

via FIRST.org ↗

90.3%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

XStream is software for serializing Java objects to XML and back again. A vulnerability in XStream versions prior to 1.4.17 may allow a remote attacker has sufficient rights to execute commands of the host only by manipulating the processed input stream. No user who followed the recommendation to setup XStream's security framework with a whitelist limited to the minimal required types is affected. The vulnerability is patched in version 1.4.17.

Affected Packages

1 total 1 fixed

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

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

Frequently Asked Questions

O3 Security · Impact-Aware SCA

Is CVE-2021-29505 in your stack?

O3 detects CVE-2021-29505 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

8.8/10

CVSS v3 base score

Vector breakdown

AV:Attack Vector

Network

AC:Attack Complexity

Low

PR:Privileges Required

Low

UI:User Interaction

None

S:Scope

Unchanged

C:Confidentiality

High

I:Integrity

High

A:Availability

High

Raw vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CWE Classification

CWE-94Code Injection CWE-502Deserialization of Untrusted Data

Weaponization

OpenSSF Scorecard

Package health score

xstream

4.3/10

Maintained2/10

Code-Review0/10

Branch-Protection0/10

Assessed Jun 1, 2026

Timeline

Disclosed

May 28, 2021

First exploit

Jun 8, 2021

Last updated

Apr 16, 2026

Identifiers

CVE-2021-29505

GHSA-7chv-rrw6-w6fc

Data from OSV.dev, enriched by O3 Security. Refreshed hourly.