CVE-2021-39144
XStream Remote Code Execution Vulnerability
XStream XStream
XStream is a simple library to serialize objects to XML and back again. In affected versions this vulnerability may allow a remote attacker 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. XStream 1.4.18 uses no longer a blacklist by default, since it cannot be secured for general purpose.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 10 March 2023. US federal agencies were required to remediate it by 31 March 2023.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 98.1%, which is higher than 99.9% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
Frequently asked questions
Is CVE-2021-39144 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2021-39144.
What does CVE-2021-39144 affect?
CVE-2021-39144 affects XStream XStream. XStream is a simple library to serialize objects to XML and back again. In affected versions this vulnerability may allow a remote attacker 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. XStream 1.4.18 uses no longer a blacklist by default, since it cannot be secured for general purpose.
How severe is CVE-2021-39144?
CVE-2021-39144 is rated HIGH with a CVSS base score of 8.5. EPSS puts the probability of exploitation in the next 30 days at 98.1%, higher than 99.9% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 31 March 2023.
How should organisations respond to CVE-2021-39144?
Apply the vendor patch for XStream XStream as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.