CVE-2021-39144
8.5, high Known exploitedXStream Remote Code Execution Vulnerability
- CVSS
- 8.5, high high CVSS v3.1
- EPSS, next 30 days
- 98% higher than 99.9% of scored CVEs
- Exploitation
- Confirmed in the wild
- Published
- 23 Aug 20215 years ago
Known exploited
CISA added this to the Known Exploited Vulnerabilities Catalog on 10 Mar 2023. US federal agencies had to remediate by 31 Mar 2023, a deadline that has passed.
Required action. Apply updates per vendor instructions.
Description
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.
Details
- Vendor
- XStream
- Product
- xstream
- Weakness
- CWE-94 (opens in a new tab)
- Status
- Analyzed
- Updated
- 17 Jun 2026
- Assigner
- security-advisories@github.com
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
References 13
Exploit code 2
Patches and fixes 3
Advisories 4
Other references 4
- lists.fedoraproject.org /archives/list/package-announce%40lists.fedoraproject.org/message/22KVR6B5IZP3BGQ3HPWIO2FWWCKT3DHP/ (opens in a new tab)
- lists.fedoraproject.org /archives/list/package-announce%40lists.fedoraproject.org/message/PVPHZA7VW2RRSDCOIPP2W6O5ND254TU7/ (opens in a new tab)
- lists.fedoraproject.org /archives/list/package-announce%40lists.fedoraproject.org/message/QGXIU3YDPG6OGTDHMBLAFN7BPBERXREB/ (opens in a new tab)
- cisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-39144 (opens in a new tab)
The kind is read from NVD's tags where present and from the shape of the URL otherwise, so treat it as a hint.
Beyond this page
Is CVE-2021-39144 in your network?
This page tells you how dangerous CVE-2021-39144 is out there. Whether it sits on one of your devices, only a scan of your own network can tell. That is what our systems do, every day, for the companies we protect.
CVE-2021-39144 is in the CISA catalogue of exploited vulnerabilities: attackers are already exploiting it.
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EXYS7600 OCELOT
Find it before attackers do
Ocelot scans your network on a schedule and reports every vulnerability it finds by its CVE identifier, with its CVSS score and how many of your hosts are affected. A finding like CVE-2021-39144 comes with the devices to patch.
Learn more about EXYS7600 OCELOT -
EXYS7950 KONDRA
Detect it if it's exploited
Until the patch is applied, Kondra monitors your network, events and endpoints in real time. It keeps an inventory of the software installed on every endpoint, and its anomaly detection rules flag what an attacker does once inside.
Learn more about EXYS7950 KONDRA
Assembled from the NVD 2.0 API, the CISA Known Exploited Vulnerabilities Catalog and FIRST EPSS. Scores are as of our last collection on 17 Oct 2026, not the live upstream state.