CVE-2021-2388Network attack vector

Sandbox escape through an undisclosed HotSpot flaw

Published Jul 20, 2021 · Updated Sep 26, 2024

Sandbox escape in Oracle Java SE 8u291, 11.0.11, and 16.0.1 allows remote attackers to take over the runtime through untrusted code. Oracle identifies HotSpot as the affected component but has not published the erroneous operation or input handling that breaks the sandbox. Exploitation requires a person to run network-delivered untrusted code in a sandboxed Java Web Start application or applet; trusted-code server deployments are excluded.

CVSS severity7.5
High
EPSS probability4.01%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Sandbox escape in Oracle Java SE 8u291, 11.0.11, and 16.0.1 allows remote attackers to take over the runtime through untrusted code. Oracle identifies HotSpot as the affected component but has not published the erroneous operation or input handling that breaks the sandbox. Exploitation requires a person to run network-delivered untrusted code in a sandboxed Java Web Start application or applet; trusted-code server deployments are excluded.

The record

CVE
CVE-2021-2388
Published
Jul 20, 2021
Updated
Sep 26, 2024
Vendor
Oracle Corporation
Product
Java Platform, Standard Edition (Java SE)
Classifications
T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 26, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Java SE:11.0.11
  2. Affected versionversion=Java SE:16.0.1
  3. Affected versionversion=Java SE:8u291
  4. Affected versionversion=Oracle GraalVM Enterprise Edition:20.3.2
  5. Affected versionversion=Oracle GraalVM Enterprise Edition:21.1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Oracle Corporation · Java Platform, Standard Edition (Java SE)version=Java SE:11.0.11; version=Java SE:16.0.1; version=Java SE:8u291; version=Oracle GraalVM Enterprise Edition:20.3.2; version=Oracle GraalVM Enterprise Edition:21.1.0

Published CVSS scores

5.1NIST NVDAV:N/AC:H/Au:N/C:P/I:P/A:P
7.5OracleCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo