SOC status:Duty analyst on shift

UK Cyber Defence
VulnerabilityAnalyzed

CVE-2021-21350

In XStream before version 1.4.16, there is a vulnerability which may allow a remote attacker to execute arbitrary code only by manipulating the processed input stream.

CRITICAL 9.8EPSS 15.2%

Does this matter?

EPSS puts the probability of exploitation in the next 30 days at 15.2%, higher than 97% of all known CVEs. Patch or mitigate before the next change window.

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 to execute arbitrary code 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.

CVSS 3.1
9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
15.23% probability · 97th percentile
Public exploits
None in Exploit-DB
CISA KEV
Not listed
Weakness
CWE-434, CWE-502
Affected
netapp/oncommand insight · apache/activemq · apache/jmeter · xstream/xstream · debian/debian linux · fedoraproject/fedora · oracle/banking enterprise default management · oracle/banking platform · oracle/banking virtual account management · oracle/business activity monitoring · oracle/communications billing and revenue management elastic charging engine · oracle/communications policy management · oracle/communications unified inventory management · oracle/retail xstore point of service · oracle/webcenter portal · oracle/weblogic server
Source
security-advisories@github.com
EPSS trend
0%10%20%3 November 2026: 15.23%3 November 20263 November 2026

EPSS 15.2% since 3 November 2026; no change recorded yet. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”. Points are recorded when the score first appears and whenever it moves by a percentage point or more.

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.