CVE-2021-39144

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.

CVSS: 8.5Highscored by the publisher (CNA)
Exploited in the wild: Yes, in CISA KEV since 10 Mar 2023CISA deadline for US federal agencies: 31 Mar 2023public exploit code
EPSS: 98.1%chance of exploitation in the next 30 daystop 0.1% of scored CVEsFIRST score of 11 Nov 2026
Fix: Patch availablesee the advisories in the references
Published: 23 Aug 2021analysed here 12 Nov 2026

Do first. Apply updates per vendor instructions. (CISA's required action for this KEV entry)

Summary

Triage

Attack surface: Server-side
Exploitable: At runtime
Attack vector: network
Weaknesses: CWE-94 Code Injection
CWE-502 Insecure Deserialization
CWE-306 Missing Authentication
Can a WAF block it?: Partly. See why

The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.

Affected products

Product	Affected versions	Vendor says fixed in
x-stream xstream	< 1.4.18Vendor says fixed in: not stated	Not stated by the vendor

As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.

Products named in our analysis

xstream:xstream
debian:debian_linux
fedoraproject:fedora
netapp:snapmanager
oracle:business_activity_monitoring
oracle:commerce_guided_search
oracle:communications_billing_and_revenue_management_elastic_charging_engine
oracle:communications_cloud_native_core_automated_test_suite
oracle:communications_cloud_native_core_binding_support_function
oracle:communications_cloud_native_core_policy
oracle:communications_unified_inventory_management
oracle:retail_xstore_point_of_service
oracle:utilities_framework
oracle:utilities_testing_accelerator
oracle:webcenter_portal

Fix and mitigation

WAF and other mitigations

Can a WAF block it? Partly. Code injection payloads are often obfuscated, so they slip past generic WAF rules.

Also consider: remove eval sinks · RASP · allow-list classes · patch

Based on the weakness type only; no CVE-specific evidence yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.

Remediation steps (AI-written)

Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.

Exploitation evidence

CISA KEV catalog: Listed since 10 Mar 2023.
CISA due date: 31 Mar 2023, the remediation deadline for US federal agencies
CISA required action: Apply updates per vendor instructions.
Public exploit code: Yes: 1 Metasploit module · 1 Nuclei template
CISA SSVC: exploitation active, automatable no, technical impact totalAssessed by CISA 6 Feb 2025 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.

Metasploit

exploit/linux/http/vmware_nsxmgr_xstream_rce_cve_2021_39144exploit, rank excellent

Nuclei

XStream 1.4.18 - Remote Code Executiondetection template, high

Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.

Timeline

23 Aug 2021Published
10 Mar 2023Added to CISA KEV (exploited in the wild)563 days (about 2 years) later
31 Mar 2023CISA remediation due date (US federal agencies)21 days later
6 Feb 2025CISA SSVC assessment: exploitation active679 days (about 2 years) later
21 Oct 2025CVE record last updated257 days (about 9 months) later
12 Nov 2026Analysed by vulneraibility.com387 days (about 1 year) later

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H

Metric	Value	What it means
Attack vector	NetworkReachable over the internet or any routable network.	Reachable over the internet or any routable network.
Attack complexity	HighNeeds specific conditions, a race or a particular configuration.	Needs specific conditions, a race or a particular configuration.
Privileges required	LowThe attacker needs basic user privileges.	The attacker needs basic user privileges.
User interaction	NoneNo victim action needed.	No victim action needed.
Scope	ChangedImpact crosses a security boundary into other components.	Impact crosses a security boundary into other components.
Confidentiality	HighTotal data disclosure possible.	Total data disclosure possible.
Integrity	HighComplete modification possible.	Complete modification possible.
Availability	HighFull outage possible.	Full outage possible.

Common questions

Is CVE-2021-39144 being exploited?

Yes. CVE-2021-39144 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.

How severe is CVE-2021-39144?

CVE-2021-39144 is rated High with a CVSS score of 8.5. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.

Is there a patch for CVE-2021-39144?

Yes. A fix has been recorded for CVE-2021-39144. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.

What does CVE-2021-39144 affect?

CVE-2021-39144 affects xstream:xstream, debian:debian_linux, fedoraproject:fedora, netapp:snapmanager, and 11 further products or versions. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.

Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.

References

NVD CVE.org CVE Details Source

13 references in the CVE record, grouped by the tags the record gives them.

Advisories (4)

lists.fedoraproject.org /archives/list/package-announce%40lists.fedoraproject.org/message/22KVR6B5IZP3BG
lists.fedoraproject.org /archives/list/package-announce%40lists.fedoraproject.org/message/QGXIU3YDPG6OGT
lists.fedoraproject.org /archives/list/package-announce%40lists.fedoraproject.org/message/PVPHZA7VW2RRSD
debian.org /security/2021/dsa-5004

Where the data on this page comes from

CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
NVD: CVSS and CPE data
CISA KEV catalog: exploitation, date added, due date
CISA Vulnrichment (ADP): SSVC decision points
FIRST EPSS: exploit probability and percentile
Metasploit Framework: exploit and scanner modules
Nuclei templates: detection templates
OSV: advisory aliases and downstream package versions

Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.

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