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CVE-2026-61891

HIGHCVSS 7.5/10EPSS 0.46%

Last modified

CVE-2026-61891 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. In Eclipse Theia versions up to and including 1.73.1, the `@theia/filesystem` backend exposes HTTP file-download endpoints (`GET /file`, `GET /files/`, `PUT /files/`) that convert a client-supplied URI directly to a filesystem path and stream the file, without confining it to the workspace or any allow-listed root. In browser (non-Electron) deployments the connection token is enforced only on WebSocket upgrades; the HTTP middleware in `@theia/core` re-issues the cookie and calls `next()` without rejecting tokenless HTTP requests, so these endpoints are reachable without a valid token. EPSS estimates a 0.46% chance of exploitation in the next 30 days.

Description

In Eclipse Theia versions up to and including 1.73.1, the `@theia/filesystem` backend exposes HTTP file-download endpoints (`GET /file`, `GET /files/`, `PUT /files/`) that convert a client-supplied URI directly to a filesystem path and stream the file, without confining it to the workspace or any allow-listed root. In browser (non-Electron) deployments the connection token is enforced only on WebSocket upgrades; the HTTP middleware in `@theia/core` re-issues the cookie and calls `next()` without rejecting tokenless HTTP requests, so these endpoints are reachable without a valid token. As a result an unauthenticated client can read any file readable by the backend process, including files outside the opened workspace (for example `/etc/hosts`, SSH keys, or tokens). Electron mode uses a separate `ElectronSecurityToken` and is not affected via this path.

Metrics

CVSS 3.1
7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS Probability
0.46%

37.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
EclipseTheia< 1.74.0

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is CVE-2026-61891?
In Eclipse Theia versions up to and including 1.73.1, the `@theia/filesystem` backend exposes HTTP file-download endpoints (`GET /file`, `GET /files/`, `PUT /files/`) that convert a client-supplied URI directly to a filesystem path and stream the file, without confining it to the workspace or any allow-listed root. In browser (non-Electron) deployments the connection token is enforced only on WebSocket upgrades; the HTTP middleware in `@theia/core` re-issues the cookie and calls `next()` without rejecting tokenless HTTP requests, so these endpoints are reachable without a valid token. As a result an unauthenticated client can read any file readable by the backend process, including files outside the opened workspace (for example `/etc/hosts`, SSH keys, or tokens). Electron mode uses a separate `ElectronSecurityToken` and is not affected via this path.
How severe is CVE-2026-61891?
CVE-2026-61891 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.46% probability of exploitation in the next 30 days.
How do I fix CVE-2026-61891?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST