CVE-2021-21345 | XStream is vulnerable to a Remote Command Execution attack

Exp

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.

Published: 2021-03-23 Last update: 2025-05-23 Assigner: [email protected] Source: [email protected]

Conclusion & alert: CVE-2021-21345 is rated High Exploit Risk (71.5/100): CVSS Medium severity, with high exploitation likelihood (EPSS 86.56%, 99th percentile). Core evidence: 1 public exploit reference(s) are indexed (Exploit-DB). Mandatory action: Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-21345

EDB-ID Source Kind Published Link
nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-21345

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-31 88.09% 86.56% -1.53%
2 2026-03-24 86.96% 88.09% +1.13%
3 2026-03-10 86.96%

Full EPSS history (61 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-21345

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.8 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
1.3 4.0 [email protected]
9.9 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
3.1 6.0 [email protected]
6.5 2.0 MEDIUM
AV:N/AC:L/Au:S/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
8.0 6.4 [email protected]

Weakness enumeration for CVE-2021-21345

GitHub Security Advisory for CVE-2021-21345

GHSA-hwpc-8xqv-jvj4 · Severity: medium · Ecosystem: maven — XStream is vulnerable to a Remote Command Execution attack

OS Trackers for CVE-2021-21345

vendor priority summary link
debian not yet assigned CVE-2021-21345 not yet assigned priority: Debian including 1 source packages (libxstream-java), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-21345
redhat high https://access.redhat.com/security/cve/CVE-2021-21345
suse high CVE-2021-21345 severity important: SUSE including 247 source package names (5.0.0-beta1.2.122:xstream-1.4.16-3.8.1, 5.1.0.6.40:xstream-1.4.16-3.8.1, …), 280 product×package rows across 32 product lines (Container suse/manager/5.0/x86_64/server, Container suse/multi-linux-manager/5.1/x86_64/server, … (32 product lines)): Known Affected 231, Fixed 49. https://www.suse.com/security/cve/CVE-2021-21345/
ubuntu medium CVE-2021-21345 medium priority: Ubuntu including 1 source packages (libxstream-java), 14 status rows across 14 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, trusty, upstream, xenial): released 14. https://ubuntu.com/security/CVE-2021-21345

Affected software / configurations for CVE-2021-21345

Vendor Product Version Raw CPE
netapp oncommand_insight cpe:2.3:a:netapp:oncommand_insight:-:*:*:*:*:*:*:*
apache activemq < 5.15.14 cpe:2.3:a:apache:activemq:*:*:*:*:*:*:*:*
apache activemq 5.16.0 cpe:2.3:a:apache:activemq:5.16.0:*:*:*:*:*:*:*
apache activemq 5.16.1 cpe:2.3:a:apache:activemq:5.16.1:*:*:*:*:*:*:*
apache jmeter < 5.5 cpe:2.3:a:apache:jmeter:*:*:*:*:*:*:*:*
xstream xstream < 1.4.16 cpe:2.3:a:xstream:xstream:*:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
debian debian_linux 11.0 cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
fedoraproject fedora 33 cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
fedoraproject fedora 34 cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
fedoraproject fedora 35 cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
oracle banking_enterprise_default_management 2.10.0 cpe:2.3:a:oracle:banking_enterprise_default_management:2.10.0:*:*:*:*:*:*:*
oracle banking_enterprise_default_management 2.12.0 cpe:2.3:a:oracle:banking_enterprise_default_management:2.12.0:*:*:*:*:*:*:*
oracle banking_platform 2.4.0 cpe:2.3:a:oracle:banking_platform:2.4.0:*:*:*:*:*:*:*
oracle banking_platform 2.7.1 cpe:2.3:a:oracle:banking_platform:2.7.1:*:*:*:*:*:*:*
oracle banking_platform 2.9.0 cpe:2.3:a:oracle:banking_platform:2.9.0:*:*:*:*:*:*:*
oracle banking_platform 2.12.0 cpe:2.3:a:oracle:banking_platform:2.12.0:*:*:*:*:*:*:*
oracle banking_virtual_account_management 14.2.0 cpe:2.3:a:oracle:banking_virtual_account_management:14.2.0:*:*:*:*:*:*:*
oracle banking_virtual_account_management 14.3.0 cpe:2.3:a:oracle:banking_virtual_account_management:14.3.0:*:*:*:*:*:*:*
oracle banking_virtual_account_management 14.5.0 cpe:2.3:a:oracle:banking_virtual_account_management:14.5.0:*:*:*:*:*:*:*
oracle business_activity_monitoring 11.1.1.9.0 cpe:2.3:a:oracle:business_activity_monitoring:11.1.1.9.0:*:*:*:*:*:*:*
oracle business_activity_monitoring 12.2.1.3.0 cpe:2.3:a:oracle:business_activity_monitoring:12.2.1.3.0:*:*:*:*:*:*:*
oracle business_activity_monitoring 12.2.1.4.0 cpe:2.3:a:oracle:business_activity_monitoring:12.2.1.4.0:*:*:*:*:*:*:*
oracle communications_billing_and_revenue_management_elastic_charging_engine 12.0.0.3.0 cpe:2.3:a:oracle:communications_billing_and_revenue_management_elastic_charging_engine:12.0.0.3.0:*:*:*:*:*:*:*
oracle communications_policy_management 12.5.0 cpe:2.3:a:oracle:communications_policy_management:12.5.0:*:*:*:*:*:*:*
oracle communications_unified_inventory_management 7.3.2 cpe:2.3:a:oracle:communications_unified_inventory_management:7.3.2:*:*:*:*:*:*:*
oracle communications_unified_inventory_management 7.3.4 cpe:2.3:a:oracle:communications_unified_inventory_management:7.3.4:*:*:*:*:*:*:*
oracle communications_unified_inventory_management 7.3.5 cpe:2.3:a:oracle:communications_unified_inventory_management:7.3.5:*:*:*:*:*:*:*
oracle communications_unified_inventory_management 7.4.0 cpe:2.3:a:oracle:communications_unified_inventory_management:7.4.0:*:*:*:*:*:*:*
oracle communications_unified_inventory_management 7.4.1 cpe:2.3:a:oracle:communications_unified_inventory_management:7.4.1:*:*:*:*:*:*:*
oracle peoplesoft_enterprise_peopletools 8.58 cpe:2.3:a:oracle:peoplesoft_enterprise_peopletools:8.58:*:*:*:*:*:*:*
oracle peoplesoft_enterprise_peopletools 8.59 cpe:2.3:a:oracle:peoplesoft_enterprise_peopletools:8.59:*:*:*:*:*:*:*
oracle retail_xstore_point_of_service 16.0.6 cpe:2.3:a:oracle:retail_xstore_point_of_service:16.0.6:*:*:*:*:*:*:*
oracle retail_xstore_point_of_service 17.0.4 cpe:2.3:a:oracle:retail_xstore_point_of_service:17.0.4:*:*:*:*:*:*:*
oracle retail_xstore_point_of_service 18.0.3 cpe:2.3:a:oracle:retail_xstore_point_of_service:18.0.3:*:*:*:*:*:*:*
oracle retail_xstore_point_of_service 19.0.2 cpe:2.3:a:oracle:retail_xstore_point_of_service:19.0.2:*:*:*:*:*:*:*
oracle webcenter_portal 11.1.1.9.0 cpe:2.3:a:oracle:webcenter_portal:11.1.1.9.0:*:*:*:*:*:*:*
oracle webcenter_portal 12.2.1.3.0 cpe:2.3:a:oracle:webcenter_portal:12.2.1.3.0:*:*:*:*:*:*:*
oracle webcenter_portal 12.2.1.4.0 cpe:2.3:a:oracle:webcenter_portal:12.2.1.4.0:*:*:*:*:*:*:*

References for CVE-2021-21345

URL Tags
http://x-stream.github.io/changes.html#1.4.16 Release Notes Third Party Advisory
https://github.com/x-stream/xstream/security/advisories/GHSA-hwpc-8xqv-jvj4 Third Party Advisory
https://lists.apache.org/thread.html/r8244fd0831db894d5e89911ded9c72196d395a90ae655414d23ed0dd%40%3Cusers.activemq.apache.org%3E Issue Tracking Mailing List Third Party Advisory
https://lists.apache.org/thread.html/r9ac71b047767205aa22e3a08cb33f3e0586de6b2fac48b425c6e16b0%40%3Cdev.jmeter.apache.org%3E Issue Tracking Mailing List Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/04/msg00002.html Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/22KVR6B5IZP3BGQ3HPWIO2FWWCKT3DHP/ Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PVPHZA7VW2RRSDCOIPP2W6O5ND254TU7/ Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGXIU3YDPG6OGTDHMBLAFN7BPBERXREB/ Mailing List Third Party Advisory
https://security.netapp.com/advisory/ntap-20210430-0002/ Third Party Advisory
https://www.debian.org/security/2021/dsa-5004 Mailing List Third Party Advisory
https://www.oracle.com//security-alerts/cpujul2021.html Third Party Advisory
https://www.oracle.com/security-alerts/cpuApr2021.html Patch Third Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html Patch Vendor Advisory
https://www.oracle.com/security-alerts/cpuoct2021.html Third Party Advisory
https://x-stream.github.io/CVE-2021-21345.html Exploit Third Party Advisory
https://x-stream.github.io/security.html#workaround Mitigation Third Party Advisory
cvelogic Threat Intelligence