Vulnerability Details CVE-2026-12609
In Eclipse Theia versions 1.66.0 and up until including 1.73.1, the `@theia/plugin-ext` backend exposes the `/hostedPlugin/:pluginId/:path(*)` HTTP endpoint, which resolves the requested file path with `path.resolve(localPath, filePath)` without verifying that the resolved path stays within the plugin's directory. An unauthenticated network attacker can send percent-encoded `../` sequences (`%2e%2e%2f`) that decode into the path parameter and escape the plugin directory, allowing arbitrary files readable by the Theia backend process to be retrieved. Plugin IDs are derived deterministically from a plugin's publisher and name, so built-in plugins serve as reliable anchors that require no prior knowledge of the target system.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.004
EPSS Ranking 34.4%
CVSS Severity
CVSS v3 Score 7.5
References
Products affected by CVE-2026-12609
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cpe:2.3:a:eclipse:theia:1.66.0
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cpe:2.3:a:eclipse:theia:1.66.1
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cpe:2.3:a:eclipse:theia:1.66.2
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cpe:2.3:a:eclipse:theia:1.67.0
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cpe:2.3:a:eclipse:theia:1.68.0
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cpe:2.3:a:eclipse:theia:1.68.1
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cpe:2.3:a:eclipse:theia:1.68.2
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cpe:2.3:a:eclipse:theia:1.69.0
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cpe:2.3:a:eclipse:theia:1.70.0
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cpe:2.3:a:eclipse:theia:1.70.1
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cpe:2.3:a:eclipse:theia:1.70.2
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cpe:2.3:a:eclipse:theia:1.71.0
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cpe:2.3:a:eclipse:theia:1.71.1
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cpe:2.3:a:eclipse:theia:1.71.2
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cpe:2.3:a:eclipse:theia:1.72.0
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cpe:2.3:a:eclipse:theia:1.72.1
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cpe:2.3:a:eclipse:theia:1.72.2
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cpe:2.3:a:eclipse:theia:1.72.3
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cpe:2.3:a:eclipse:theia:1.73.0
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cpe:2.3:a:eclipse:theia:1.73.1