Vulnerability

CVE-2021-39144

High· 8.5KEVEXPLOITCVSS8.5EPSS94%

.rules3/5

XStream Remote Code Execution Vulnerability

XStream contains a remote code execution vulnerability that allows an attacker to manipulate the processed input stream and replace or inject objects that result in the execution of a local command on the server. This vulnerability can affect multiple products, including but not limited to VMware Cloud Foundation.

Threat signal

100/100

Severe

Severity

high

CVSS

8.5

EPSS

94%

Active

KEV

CISA KEV — actively exploited

1170d overdue

AffectedXStream — XStream

Added to KEV

2023-03-10

Federal patch due (BOD 22-01)

2023-03-31

Required action (CISA verbatim)

Apply updates per vendor instructions.

Vendor advisory + references

CISA description: “XStream contains a remote code execution vulnerability that allows an attacker to manipulate the processed input stream and replace or inject objects that result in the execution of a local command on the server. This vulnerability can affect multiple products, including but not limited to VMware Cloud Foundation.”

CVSS

v3.1Open in FIRST calculator →

8.5/ 10HIGHCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H

Attack VectorNetworkExploitable remotely over the internet — no local access needed.
Attack ComplexityHighRequires conditions outside attacker's control (race, brute-force, configuration
Privileges RequiredLowStandard user privileges sufficient.
User InteractionNoneFully automated — no victim action needed.
ScopeChangedImpact extends beyond the vulnerable component (e.g. sandbox escape).
Confidentiality ImpactHighTotal disclosure of sensitive data.
Integrity ImpactHighTotal compromise of integrity — full data modification possible.
Availability ImpactHighTotal loss of availability — full DoS possible.

EPSS

Exploit prediction · 30-day horizonFIRST.org →

94.3%

probability of exploitation in next 30 days

p100

higher than 100% of all CVEs

3-day trend↑ 0pp

Statistically about to be weaponized — top-tier triage urgency.

Vendor VEX

No VEX statements published for CVE-2021-39144. Vendors publish VEX (Vulnerability Exploitability eXchange) to assert per-product whether a CVE is actually exploitable in their distribution.

SSVCAct

Active exploitation with total impact on essential/support systems

exploitation: active
automatable: yes
impact: total
mission: support

Lifecycle

2021-12-10Vendor advisory · amazon-linuxALAS2-2021-1729 — ALAS2-2021-1729 (important): xstream
2023-03-10Added to CISA KEVransomware: Unknown
2023-03-10Public exploit observedmetasploit
2023-03-10Published
2023-03-31Federal patch due (BOD 22-01)
2026-06-12Last modified1 source

Entity graph

2 nodes · 1 edges · click to pivot

CVEActorVendor advisoryIOCNews

Vendor advisories

amazon-linuxALAS2-2021-1729ALAS2-2021-1729 (important): xstream

No source-event history recorded yet. New revisions will appear here as ingestors re-fetch this CVE.