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CVE-2021-21345

XStream is vulnerable to a Remote Command Execution attack

CVSS 3.1 Medium 5.8

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

Description

XStream is a Java library to serialize objects to XML and back again. In XStream before version 1.4.16, there is a vulnerability which may allow a remote attacker who 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. If you rely on XStream's default blacklist of the Security Framework, you will have to use at least version 1.4.16.

Official description from the CVE record, published by GitHub_M. Copyright © 1999-2026 The MITRE Corporation. See /security/cve/legal for the CVE license. View the record on cve.org

Key data

CVSS 3.1 Medium 5.8

Score published by GitHub_M in the CVE record.

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

  • Attack vector: Network

    The vulnerable component can be reached over a network, possibly from the Internet.

  • Attack complexity: High

    The attack depends on conditions outside the attacker's control, so it takes preparation.

  • Privileges required: Low

    A basic user account is needed.

  • User interaction: Required

    A user has to do something first, such as opening a file or following a link.

  • Scope: Changed

    The impact can reach other components beyond the vulnerable one.

  • Confidentiality impact: None

    No effect on the secrecy of data.

  • Integrity impact: High

    Serious or total effect on the trustworthiness of data.

  • Availability impact: None

    No effect on availability.

CVSS is owned and managed by FIRST.Org, Inc. (FIRST) and is used by permission. Each CVSS score on this site is shown together with its vector string, as published in the CVE record by the source named next to it. Learn more at first.org/cvss.

EPSS

Exploit Prediction Scoring System by FIRST: an estimate of the probability that exploitation activity will be observed in the next 30 days.
Score
0.72324 (72.3% probability)
Percentile
99.4%
Scores of
Nov 10, 2026
Model
v2026.06.15

CISA assessment as of Oct 7, 2026

Stakeholder-Specific Vulnerability Categorization (SSVC) decision points added by CISA.
Automatable
no
Technical impact
total

Weakness (CWE)

CWE catalog version 5.0.
CWE names: Copyright © 2006-2026, The MITRE Corporation. See /security/cve/legal for the CWE license.
  • CWE-94Improper Control of Generation of Code
  • CWE-502Deserialization of Untrusted Data

Affected products

Products listed in the CVE record, as the CNA published them.

  • x-stream xstream

    • affected: < 1.4.16

References

Links listed in the CVE record. They lead to other sites, which CubePath does not control.

Timeline

  1. ID reserved
  2. Record published
  3. Record last updated

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Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 19:52 UTC. Sources and licenses