CVE-2026-12609
CVSS v3
7.5
HIGH
EPSS Score
1.6 %
exploit probability, as of 2026-10-13
CISA KEV
No
known exploited
Exploitation
—
SSVC status
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Affected and fixed versions
Neither OSV.dev nor the vendor advisories we read list affected versions for CVE-2026-12609 yet.
Description
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.
Technical details
- CVSS v3 Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- Published
- 2026-08-05
- Last Modified
- 2026-08-06
Frequently asked questions
What is 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.
Is CVE-2026-12609 actively exploited?
Active exploitation of CVE-2026-12609 has not been confirmed. Its EPSS score was 1.6% on 2026-10-13, the estimated probability of exploitation in the next 30 days.
What is the CVSS score for CVE-2026-12609?
CVE-2026-12609 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
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