CVE-2020-27221
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn Eclipse OpenJ9 up to and including version 0.23, there is potential for a stack-based buffer overflow when the virtual machine or JNI natives are converting from UTF-8 characters to platform encoding.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceEclipse OpenJ9 versions 0.23 and earlier contain a stack-based buffer overflow vulnerability in the UTF-8 to platform encoding conversion path. The overflow occurs within the virtual machine or JNI native code responsible for character encoding transformation, potentially allowing an attacker to overwrite stack memory and execute arbitrary code.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data<= 0.23.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Confirm Eclipse OpenJ9 is the JVM in useRun 'java -version' and examine the output. Look for 'OpenJ9' in the JVM name or vendor string.Affected if The output shows Eclipse OpenJ9 as the runtime (as opposed to HotSpot, GraalVM, or other JVMs)
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Identify the OpenJ9 version numberRun 'java -XshowSettings:all -version 2>&1 | grep -i version' or check the jvm.cfg file in the JVM lib directory. The version typically appears in the path or binary name (e.g., openj9-0.23.0).Affected if A version number is returned and it matches the OpenJ9 naming pattern
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Compare installed version against affected rangeCompare the identified version to '<= 0.23.0'. OpenJ9 versions are formatted as 0.x.x (e.g., 0.21.0, 0.23.0).Affected if The version is 0.23.0 or any earlier 0.x.x release (0.21.0, 0.20.0, etc.)
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Verify UTF-8 conversion is in use (optional context)Review application code or runtime arguments for character encoding operations involving UTF-8 to platform encoding (e.g., String.getBytes(), charset conversion, JNI native code handling strings).Affected if The application performs UTF-8 to platform encoding conversions (this is the vulnerable code path)
You are affected if your environment runs Eclipse OpenJ9 version 0.23.0 or any earlier version (0.x.x <= 0.23.0) and performs UTF-8 to platform encoding conversions.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedUpgrade Eclipse OpenJ9 to version 0.24 or later to resolve the stack-based buffer overflow in the UTF-8 conversion code.
OpenJ9 0.24.0 or later
- Identify the current OpenJ9 version in use by checking the JVM version string (java -version)
- Upgrade OpenJ9 to version 0.24.0 or later, as versions after 0.23.0 contain the fix for this stack-based buffer overflow vulnerability
- Verify the upgrade was successful by running java -version and confirming the new version number
- Test applications to ensure compatibility with the upgraded JVM
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation8.0 h
- Implementation16.0 h
- Testing12.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-27221 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-27221 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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