SOC status:Duty analyst on shift

UK Cyber Defence
VulnerabilityAnalyzed

CVE-2021-21345

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.

CRITICAL 9.9EPSS 72.3%

Does this matter?

EPSS puts the probability of exploitation in the next 30 days at 72.3%, higher than 99% 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 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.

CVSS 3.1
9.9 CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
EPSS
72.32% probability · 99th percentile
Public exploits
None in Exploit-DB
CISA KEV
Not listed
Weakness
CWE-94, CWE-502, CWE-78
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/peoplesoft enterprise peopletools · oracle/retail xstore point of service · oracle/webcenter portal
Source
security-advisories@github.com
EPSS trend
0%38%75%26 October 2026: 72.32%26 October 202626 October 2026

EPSS 72.3% since 26 October 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.