Upgrading to Rust 1.94.1: A Comprehensive Guide

Overview

Rust 1.94.1 is a point release that addresses several regressions introduced in Rust 1.94.0, along with a security fix in Cargo. This guide will walk you through the update process, explain what’s changed, and help you avoid common pitfalls. Whether you’re a seasoned Rustacean or new to the language, following these steps will ensure you get the latest stable version with minimal friction.

Prerequisites

Before you begin, make sure you have the following:

• Rust installed via rustup – This is the recommended way to manage Rust versions. If you haven’t installed Rust yet, visit rustup.rs and follow the instructions for your operating system.
• An active internet connection – You’ll need to download the new toolchain components.
• Basic familiarity with the command line – Updating is done through terminal commands.
• Optional: current Rust version check – Run rustc --version to see your current version. If it’s already 1.94.1, you’re all set!

Step-by-Step Instructions

Step 1: Update Rust via rustup

Open your terminal (Command Prompt on Windows, Terminal on macOS/Linux) and run:

rustup update stable

This command tells rustup to fetch and install the latest stable release — in this case, Rust 1.94.1. rustup will download the toolchain components and apply the update automatically.

What happens behind the scenes?
rustup checks the current stable channel, compares it with your installed version, and downloads the delta if needed. The process typically takes less than a minute.

Step 2: Verify the Installation

After the update completes, confirm that you are now on the correct version:

rustc --version

You should see output similar to:

rustc 1.94.1 (e.g., 5d59182c6 2025-04-10)

Also check Cargo:

cargo --version

Expected output:

cargo 1.94.1 (e.g., 5d59182c6 2025-04-10)

Step 3: Understand What Changed in 1.94.1

Let’s break down the key fixes included in this release.

Fix for std::thread::spawn on wasm32-wasip1-threads

If you target WebAssembly with the wasm32-wasip1-threads target, you may have encountered a regression in 1.94.0 that caused std::thread::spawn to fail. This has been corrected in 1.94.1.

Removal of Unstable Methods from std::os::windows::fs::OpenOptionsExt

Rust 1.94.0 inadvertently added new unstable methods to the OpenOptionsExt trait on Windows. Since the trait is not sealed (i.e., it can be implemented by external code), adding methods with default implementations is a breaking change. The Rust team removed these methods to preserve backward compatibility. If you relied on them, you’ll need to wait for a future stable release.

Clippy: Fixed ICE in match_same_arms

Clippy, the Rust linter, had an internal compiler error (ICE) when analyzing match_same_arms in certain cases. That bug is now resolved, so you can run clippy without unexpected crashes.

Cargo: Downgrade curl-sys to 0.4.83

Cargo depends on curl-sys for HTTP operations. Version 0.4.84 introduced certificate validation errors on some FreeBSD systems. To fix this, the Cargo maintainers reverted to 0.4.83. If you use FreeBSD and experienced SSL/TLS issues, they should be resolved after updating.

Security Fix: Update tar to 0.4.45

The tar crate used by Cargo was updated to version 0.4.45, addressing two security vulnerabilities:

• CVE-2026-33055
• CVE-2026-33056

These CVEs affect how tar archives are processed. Users of crates.io are not affected because the registry uses a different mechanism. However, if you use cargo package or cargo publish with custom archives, the fix is important.

Step 4 (Optional): Test Your Projects

After updating, compile and run your Rust projects to ensure they work. Use:

cargo check

or

cargo build

Pay attention to any warnings or errors, especially if you were affected by the regressions.

Common Mistakes

• Forgetting to run the update command – Rust does not auto-update. You must explicitly run rustup update stable.
• Using the wrong channel – If you have previously switched to nightly or beta, rustup update stable will not update your active toolchain unless you switch back. Use rustup default stable if needed.
• Ignoring FreeBSD certificate errors – If you are on FreeBSD and see SSL errors after updating to 1.94.0, the downgrade in 1.94.1 should fix them. If not, check your system’s CA certificates.
• Assuming Cargo’s tar security fix applies to all use cases – While crates.io is safe, if you use cargo package with custom archives, you are vulnerable until you update.
• Not verifying the version after update – Always double-check with rustc --version; a silent failure could leave you on an older version.

Summary

Rust 1.94.1 is a critical point release that fixes three regressions from 1.94.0 and addresses a security vulnerability in Cargo’s tar handling. Updating is straightforward: run rustup update stable and confirm the version. Pay special attention if you use WebAssembly (wasm32-wasip1-threads), Windows filesystem traits, or are a FreeBSD user. The Rust community and contributors made this release possible, and staying up-to-date ensures you benefit from their hard work.

For a complete list of changes, refer to the Rust Blog.