CVE-2023-40030 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in cargo. A fix is available for cargo — see the affected versions and patch details below.
Malicious dependencies can inject arbitrary JavaScript into cargo-generated timing reports
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-40030.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
cargoReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
The Rust Security Response WG was notified that Cargo did not escape Cargo feature names when including them in the report generated by cargo build --timings. A malicious package included as a dependency may inject nearly arbitrary HTML here, potentially leading to XSS if the report is subsequently uploaded somewhere.
The severity of this vulnerability is "low" for users relying on dependencies from git, local paths, or alternative registries. Users who solely depend on crates.io are unaffected.
Note that by design Cargo allows code execution at build time, due to build scripts and procedural macros. The vulnerability in this advisory allows performing a subset of the possible damage in a harder to track down way. Your dependencies must still be trusted if you want to be protected from attacks, as it's possible to perform the same attacks with build scripts and procedural macros.
Overview
Rust 1.60.0 introduced cargo build --timings, which produces a report of how long the different steps of the build process took. It includes lists of Cargo features for each crate.
Prior to Rust 1.72, Cargo feature names were allowed to contain almost any characters (with some exceptions as used by the feature syntax), but it would produce a future incompatibility warning about them since Rust 1.49. crates.io is far more stringent about what it considers a valid feature name and has not allowed such feature names.
As the feature names defined in the Cargo.toml file were included unescaped in the timings report, they could be used to inject Javascript into the page. For example with a feature name like features = ["<img src='' onerror=alert(0)"]. If this report were subsequently uploaded to a domain that uses credentials, the injected Javascript could access resources from the website visitor.
This issue was fixed by turning the future incompatibility warning into an error.
Affected versions
The vulnerability is present in all versions of Cargo after and including 1.60.0. Rust 1.72, to be released on August 24, will include a fix for it.
Users whose dependencies are entirely on crates.io are unaffected.
Mitigations
We recommend users always excercise care in which package they download, by only including trusted dependencies in their projects. Please note that even with these vulnerabilities fixed, by design Cargo allows arbitrary code execution at build time thanks to build scripts and procedural macros: a malicious dependency will be able to cause damage regardless of these vulnerabilities.
crates.io has server-side checks preventing this attack, and there are no packages on crates.io exploiting these vulnerabilities. crates.io users still need to excercise care in choosing their dependencies though, as remote code execution is allowed by design there as well.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | cargo | ≥ 1.60.0&&< 1.72 | 1.72cargo update -p cargo --precise 1.72 |
Affected Products
rustrust-langDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for cargo, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update cargo to 1.72 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-40030 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is CVE-2023-40030 in your dependencies?
Find it across crates.io, including transitive dependencies.