dbcve.org
Java Virtual MachineApplication · Microsoft

CVE-1999-0766

HIGH · 9.3 CVSS v2.0 Published 1999-10-21
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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 · unedited
The Microsoft Java Virtual Machine allows a malicious Java applet to execute arbitrary commands outside of the sandbox environment.

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 confidence

The Microsoft Java Virtual Machine contains a sandbox escape vulnerability that allows a malicious Java applet to bypass Java security restrictions and execute arbitrary commands on the host system with the privileges of the user running the applet.

MitigationDisable or remove the Microsoft Java Virtual Machine and replace with a current, supported JVM implementation such as Oracle Java, OpenJDK, or IBM JRE. Ensure Java browser plugins are disabled to prevent applet-based attacks.

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
Java Virtual MachineApplication
Affected:all versions

CVSS 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
M
Authentication
None
Confidentiality
Complete
Integrity
Complete
Availability
Complete

AV:N/AC:M/Au:N/C:C/I:C/A:C

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 checks

Work through these to decide whether this CVE applies to you.

  1. Check for Microsoft Java VM installation files
    Search the filesystem for MSJVM-related executables: msjavaw.exe, java.exe, javaw.exe in common locations such as C:\Windows\System32, C:\Program Files\Microsoft Java VM, or C:\Windows\Java. Use command: dir /s C:\msjav*.exe 2>nul
    Affected if Any MSJVM executable files are found on the system
  2. Check Windows registry for Microsoft Java VM
    Query the Windows registry for MSJVM entries. Run: reg query "HKLM\SOFTWARE\Microsoft\Java VM" or reg query "HKLM\SOFTWARE\Microsoft\MSJava"
    Affected if Registry keys under Microsoft Java VM or MSJava are present
  3. Verify Java installation vendor
    If Java is installed, open a command prompt and run: java -version. Examine the vendor information in the output
    Affected if The output shows 'Microsoft' as the Java VM vendor
  4. Check for Java browser plugin
    Examine installed browser extensions or plugins. In Internet Explorer, go to Internet Options > Security > Custom Level > Java permissions. Look for Microsoft VM Java permissions settings
    Affected if Browser is configured to allow Microsoft VM Java applets or ActiveX controls

A system is affected if Microsoft Java Virtual Machine (any version) is installed, as all versions of this deprecated product are vulnerable to the sandbox escape.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Disable or remove the Microsoft Java Virtual Machine and replace with a current, supported JVM implementation such as Oracle Java, OpenJDK, or IBM JRE. Ensure Java browser plugins are disabled to prevent applet-based attacks.

Recommended fix High confidence

Replace Microsoft Java Virtual Machine with a currently supported JRE/JDK (Oracle JDK, OpenJDK, or AdoptOpenJDK)

  1. 1. Identify all systems still running the Microsoft Java Virtual Machine
  2. 2. Uninstall or remove the Microsoft Java Virtual Machine from all affected systems
  3. 3. Install a currently supported Java runtime environment (such as Oracle JDK, OpenJDK, or AdoptOpenJDK)
  4. 4. Verify that legacy Java applets are not required for business operations; if they are, plan migration to modern technologies
  5. 5. Ensure browsers have Java browser plugins disabled or removed (modern browsers have removed Java plugin support)
  6. 6. Scan for and remove any remaining instances of the Microsoft JVM
Caveat Legacy Java applets relying on the Microsoft JVM-specific APIs may require rewriting; verify compatibility of any Java applications with the new JRE

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Java Virtual Machine Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-1999-0766 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • 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
  • No spam, self-promotion, credentials, or personal data