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Openshift Dev SpacesApplication · Redhat

CVE-2026-12856

HIGH · 8.8 CVSS v3.1 Published 2026-06-29
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges 8 weeks old

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
A flaw was found in the vscode-java extension, which provides Java language support for Visual Studio Code. The extension incorrectly trusts all Markdown content in JavaDoc hovers, allowing a malicious Java file to include hidden commands. If a user clicks a specially crafted link within a JavaDoc hover popup, an attacker can execute arbitrary VS Code commands, which can lead to full system compromise in trusted workspaces.

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 vscode-java extension renders JavaDoc content as Markdown in hover tooltips without sanitizing executable content. Attackers can embed malicious VS Code command links within JavaDoc comments that execute arbitrary commands when users click them, leading to full system compromise in trusted workspaces.

MitigationThe extension vendor should implement proper sanitization of Markdown content in JavaDoc hovers to strip or disable command links (e.g., href='command:...'), and users should avoid opening untrusted Java projects until the patch is applied.

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
Openshift Dev SpacesApplication
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
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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 checks

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

  1. Identify OpenShift Dev Spaces environment
    Check if the environment is Red Hat OpenShift Dev Spaces by looking for the Dev Spaces dashboard URL pattern (typically at 'che---next.apps.*') or checking for the 'CHE_NAMESPACE' environment variable commonly set in Dev Spaces pods.
    Affected if The environment is running OpenShift Dev Spaces (any version)
  2. Verify vscode-java extension is installed
    In the VS Code instance within Dev Spaces, open the Extensions view and search for 'Language Support for Java by Red Hat' or 'vscode-java'. Check if it shows as installed and enabled.
    Affected if The vscode-java extension is installed and enabled in the Dev Spaces workspace
  3. Check workspace trust status
    In VS Code, look for the workspace trust indicator in the bottom-left corner of the status bar (shield icon) or check File > Preferences > Settings > Workspace > Trust > Enabled. Determine if the current workspace is marked as trusted.
    Affected if The workspace is set to 'Trusted', allowing extensions to execute commands with elevated privileges
  4. Inspect Java source files for JavaDoc with hyperlinks
    Search the workspace Java files for JavaDoc comments containing markdown link syntax such as '[text](command:extension.command)' or '[label](vscode://command)' patterns, especially in public class/method documentation.
    Affected if Java files contain JavaDoc with markdown links that could trigger arbitrary VS Code commands when hovered and clicked

A user is affected if they are running OpenShift Dev Spaces with the vscode-java extension enabled in a trusted workspace and open or interact with Java files containing malicious JavaDoc comments with crafted command links.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

The extension vendor should implement proper sanitization of Markdown content in JavaDoc hovers to strip or disable command links (e.g., href='command:...'), and users should avoid opening untrusted Java projects until the patch is applied.

Fix this in Openshift Dev Spaces Scoped from the published advisory
  • Consultation2.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,290
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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-2026-12856 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
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