The open-source Rust language is known for its focus on safety and secure builds, but in 2023, a nasty vulnerability slipped through the cracks—affecting Rust’s beloved package manager: Cargo. In this post, we’ll break down CVE-2023-38497 in simple terms, provide code snippets, analyze the risks, and show you how the exploit works. Plus, you’ll get links to official advisories and practical fixes for your workstation or development environment.
What Is CVE-2023-38497?
CVE-2023-38497 is a local privilege escalation vulnerability in Cargo, the package manager and build tool for Rust. Before version .72.2 (including Cargo that’s bundled with Rust up to version 1.71.1), Cargo failed to respect the umask settings on UNIX-like systems when extracting crate archives.
This means, files extracted from crates could be left world-writable, making it easy for another user on the same machine to tamper with your project’s source code _after_ you downloaded your dependencies but _before_ you build or run them.
Official RustSec Advisory:
https://rustsec.org/advisories/RUSTSEC-2023-0073.html
Cargo Announcement:
https://github.com/rust-lang/cargo/security/advisories/GHSA-gq9j-f539-7555
The Problem, in Plain English
Imagine you’re on a shared computer—maybe at work, university, or running a build server. You use Rust and you run cargo build in your project.
Cargo downloads your dependencies from crates.io.
- Cargo extracts those dependency files into your local cache (usually in ~/.cargo).
Cargo compiles your project using those files.
But old versions of Cargo (before .72.2) extract those files with _permissions that ignore your operating system’s “umask”_—which tells the system who can read or write to files. The default result: other local users can write to your dependencies!
This means a mischievous user on the same system could _quietly_ swap out a dependency’s code between the download and the compile steps.
Code Example: Why This Is Dangerous
Let’s make it real with an example. Suppose your crate depends on the popular serde library.
Here’s your Cargo.toml
[dependencies]
serde = "1."
You run
cargo build
Cargo downloads and extracts serde's code into
~/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1..x/
A local attacker can now run
echo 'panic!("Hacked by local user!")' >> ~/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1..x/src/lib.rs
Or even sneak in a malicious build.rs script, backdoor, or shell command.
When you run cargo build again, you are compiling and linking tainted code—without any clue.
Cargo downloads and extracts dependencies, which have world-writable permissions.
3. Attacker (another user on the same computer) notices the extraction and modifies a dependency’s source file:
`bash
echo 'println!("This build is compromised!");' >> ~/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1..x/src/lib.rs
`
4. Victim next builds or runs their code. The injected code is now part of their project—they could get a backdoor, sensitive data leak, or anything the attacker writes.
5. Victim and everyone else on the system is now at risk _until_ the cache is wiped and Rust/Cargo are updated.
The Official Fix
- Cargo .72.2 (shipped with Rust 1.71.1) fixes the bug: extracted files respect your umask, so they're not left world-writable.
- Plus: The new Cargo _purges_ old extracted caches made by older, vulnerable Cargo versions, so you're not left with legacy risk.
Commit reference:
https://github.com/rust-lang/cargo/pull/12201
Upgrade now!
rustup update
Or make sure your version is at least
cargo --version
# cargo .72.2 (or higher)
`bash
chmod -R go-rwx ~/.cargo
Further References
- Rust CVE-2023-38497 Security Advisory
- Cargo GHSA-gq9j-f539-7555 Advisory
- Fix Commit on GitHub
If you can’t update, lock down your .cargo directory to prevent local tampering.
This vulnerability shows even the safest tools can have overlooked security holes—so keep your toolchain fresh, and keep building safe Rust software.
Thanks for reading! Questions? Comments? Drop them below or visit The Rust Users Forum.
Timeline
Published on: 08/04/2023 16:15:00 UTC
Last modified on: 08/17/2023 19:15:00 UTC