High [CVE-2026-12856] Command Injection vulnerability in the JavaDoc hover provider of the vscode-java extension
This high-severity Red Hat Linux advisory covers CVE-2026-12856 affecting Red Hat OpenShift Dev Spaces 3.29.
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Summary
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.
The Red Hat Product Security team has assessed the severity of this vulnerability as Important, given that it requires a user to open a malicious Java source file and interact with a hover popup. Successful exploitation allows an attacker to execute arbitrary commands within the context of the VS Code editor and potentially the underlying operating system.
The vulnerability's root cause is the over-trusting of Markdown content returned by the Java language server, which fails to isolate extension-generated trusted links from attacker-controlled JavaDoc content. Weakness: CWE-88.
Affected Red Hat products: Red Hat OpenShift Dev Spaces 3.29. Red Hat fixing advisory: RHSA-2026:36820.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 21 days ago·verify at source
- devspaces/pluginregistry-rhel9:1782989367
- RHSA-2026:36820
Official advisory · high-confidence parse· fetched 21 days ago·verify at source
Mitigation checklist
- To mitigate this issue, users should avoid opening or interacting with untrusted Java projects or files within Red Hat OpenShift Dev Spaces. Exercise caution and refrain from clicking on unfamiliar links presented in JavaDoc hover popups, particularly when working with code from unverified sources. Disabling the `vscode-java` extension when not actively engaged in Java development can further reduce exposure, though this will impact Java-related functionality.
Official advisory · high-confidence parse· fetched 21 days ago·verify at source
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