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CRITICAL

CVE-2021-21342

CVSS v3

9.1

CRITICAL

EPSS Score

50.0 %

exploit probability, as of 2026-10-19

CISA KEV

No

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • activemqBitnamiall versions · fixed in 5.15.14
  • com.thoughtworks.xstream:xstreamMavenall versions · fixed in 1.4.16

Vendor advisories

  • CVE-2021-21342 Red Hat Product Security6 products fixed · 14 known affected

    XStream: SSRF via crafted input stream

    xstream as a component of Red Hat BPM Suite 6 · xstream as a component of Red Hat Enterprise Linux 7 · xstream-javadoc as a component of Red Hat Enterprise Linux 7

  • RHSA-2021:5134 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: Red Hat Fuse 7.10.0 release and security update

  • RHSA-2021:4918 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: Red Hat Integration Camel-K 1.6 release and security update

  • RHSA-2021:4767 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: Red Hat Integration Camel Extensions for Quarkus GA security update

  • RHSA-2021:2476 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: Red Hat Decision Manager 7.11.0 security update

  • RHSA-2021:2475 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: Red Hat Process Automation Manager 7.11.0 security update

1 more advisory

Full record on NVD

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 where the processed stream at unmarshalling time contains type information to recreate the formerly written objects. XStream creates therefore new instances based on these type information. An attacker can manipulate the processed input stream and replace or inject objects, that result in a server-side forgery request. 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.

Technical details

Published
2021-03-23

Frequently asked questions

What is CVE-2021-21342?

XStream is a Java library to serialize objects to XML and back again. In XStream before version 1.4.16, there is a vulnerability where the processed stream at unmarshalling time contains type information to recreate the formerly written objects. XStream creates therefore new instances based on these type information. An attacker can manipulate the processed input stream and replace or inject objects, that result in a server-side forgery request. 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.

Is CVE-2021-21342 actively exploited?

Active exploitation of CVE-2021-21342 has not been confirmed. Its EPSS score was 50.0% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-21342?

CVE-2021-21342 has a CVSS v3 base score of 9.1 (CRITICAL severity).

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