Ruby LSP has arbitrary code execution through branch setting

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

7.1 · CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-34060: 0.50% estimated exploitation activity in the next 30 days; percentile 42.70 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The rubyLsp.branch VS Code workspace setting was interpolated without sanitization into a generated Gemfile, allowing arbitrary Ruby code execution when a user opens a project containing a malicious .vscode/settings.json. Other editors that support workspace setting that get automatically applied upon opening the editor and trusting the workspace are also impacted since the server is the component that performs the interpolation. Details The branch CLI argument passed to the ruby-lsp server was interpolated in the generated .ruby-lsp/Gemfile without sanitization. Editors that allow defining settings saved at the workspace level (e.g.: .vscode/settings.json) that gets automatically applied open the possibility to craft a malicious repository that once opened and trusted in the editor would run arbitrary code. Impact Code execution with the privileges of the user who opens the malicious project. Ruby LSP assumes workspace code is trusted and so opening the editor on an…

Published by the source

27 Mar 2026, 19:43 UTC

Last modified by the source

31 Mar 2026, 18:41 UTC

Source last checked

26 Oct 2026, 15:51 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-c4r5-fxqw-vh93

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# Patch Next advisory brief: CVE-2026-34060

Advisory: Ruby LSP has arbitrary code execution through branch setting
IDs: CVE-2026-34060, GHSA-c4r5-fxqw-vh93
Record: https://patchnext.com/advisories/cve-2026-34060 (revision 1, source checked 26 Oct 2026, 15:51 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: ruby-lsp 0.26.9. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems ruby-lsp: affected < 0.26.9; fixed in 0.26.9

## Suggested inspection (read-only)
- RubyGems ruby-lsp: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on ruby-lsp.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-c4r5-fxqw-vh93 (GitHub-reviewed advisory GHSA-c4r5-fxqw-vh93 lists affected ranges: RubyGems ruby-lsp >=0 <0.26.9)

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