How to fix or mitigate CVE-2026-34060?

Within 24 hours: Audit inventory of ruby-lsp gem and VS Code extension versions across development environments. Within 7 days: Update ruby-lsp gem to version 0.26.9 or later and VS Code ruby-lsp extension to version 0.10.2 or later on all developer machines and CI/CD systems. Within 30 days: Implement code review policy requiring examination of .vscode/settings.json and Gemfile entries before trusting new repositories; conduct developer training on workspace trust risks.

CVE-2026-34060

Q: What is the CVSS score of CVE-2026-34060?

CVE-2026-34060 has a CVSS 4.0 base score of 7.1 (High). CVSS vector: 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. EPSS exploitation probability: 0.0%.

HIGH

Code Injection (CWE-94)

2026-03-27 https://github.com/Shopify/ruby-lsp

GHSA-c4r5-fxqw-vh93

RCE Code Injection

7.1

CVSS 4.0 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

7.1 HIGH

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack Vector

Local

Attack Complexity

Low

Privileges Required

None

User Interaction

Scope

Lifecycle Timeline

Patch released

Mar 31, 2026 - 21:13 nvd

Patch available

Analysis Generated

Mar 27, 2026 - 19:45 vuln.today

CVE Published

Mar 27, 2026 - 19:43 nvd

HIGH 7.1

DescriptionGitHub Advisory

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 untrusted workspace can lead to executing potentially dangerous code.

Remediation

The rubyLsp.branch setting has been removed entirely. VS Code extensions auto-update by default, so most users will receive the fix without action. Users who have disabled auto-updates should update to extension version >= 0.10.2.

The branch CLI flag was also entirely removed from the ruby-lsp gem. For users that don't add ruby-lsp to their Gemfiles, the server should auto-update. Users with the ruby-lsp in the Gemfile and locked to a specific version should update to >= 0.26.9.

AnalysisAI

Ruby Language Server (ruby-lsp) allows arbitrary code execution when opening malicious projects. The vulnerability exploits unsanitized interpolation of the rubyLsp.branch workspace setting into a generated Gemfile, enabling attackers to embed malicious Ruby code in .vscode/settings.json that executes when users open and trust the workspace. Affects ruby-lsp gem < 0.26.9 and VS Code extension < 0.10.2. No active exploitation or public POC currently identified at time of analysis, but the attack requires only social engineering to trick developers into opening a crafted repository.

Technical ContextAI

This vulnerability stems from improper neutralization of special elements (CWE-94: Code Injection) in the ruby-lsp language server's Gemfile generation logic. The server accepts a branch parameter via the rubyLsp.branch setting and directly interpolates it into a dynamically generated .ruby-lsp/Gemfile without input validation or sanitization. In VS Code and compatible editors, workspace settings from .vscode/settings.json are automatically applied when users trust a workspace. An attacker can craft a malicious repository containing a .vscode/settings.json with embedded Ruby code in the branch setting value, such as backtick commands or system calls. When the victim opens and trusts the project, the language server generates the Gemfile with the unsanitized input, causing the Ruby interpreter to execute the injected code during Gemfile evaluation. The affected package pkg:rubygems/ruby-lsp is a Language Server Protocol implementation for Ruby that integrates with editors like VS Code to provide IDE features such as autocomplete and diagnostics.

RemediationAI

Update the ruby-lsp gem to version 0.26.9 or later and the Ruby LSP VS Code extension to version 0.10.2 or later. For most users, the VS Code extension will auto-update automatically as auto-updates are enabled by default; verify the installed version in the Extensions panel and manually update if necessary by searching for Ruby LSP and clicking Update. For users who include ruby-lsp in their project Gemfile with a locked version, update the Gemfile to specify gem 'ruby-lsp', '>= 0.26.9' and run bundle update ruby-lsp. For users who do not add ruby-lsp to their Gemfiles, the server component should auto-update when the VS Code extension updates. The vendor has removed the vulnerable rubyLsp.branch setting entirely from the extension and the branch CLI flag from the gem, eliminating the attack vector. As an additional security practice, developers should exercise caution when opening and trusting workspaces from unfamiliar or untrusted sources, as workspace settings can modify development environment behavior. Review .vscode/settings.json files in external repositories before trusting workspaces. Full remediation guidance and security advisory available at https://github.com/Shopify/ruby-lsp/security/advisories/GHSA-c4r5-fxqw-vh93.