Rust Supply Chain Attack Puts Build-Time Malware in Crates with 245 Million Downloads

Key Highlights

• "While the malicious versions of axios were removed from the npm registry within three hours of their release, the scope of the compromise is estimated to be broad, as the package has over 100 million weekly downloads," GTIG and Mandiant said in a July 30 report recommending cooling windows on newly published third-party assets.
• "We do not believe the author of arrayref to be acting maliciously, but their computer or credentials are likely compromised, and we are attempting to contact them," the Rust Security Response Team said.
• 9 within the same minute as the malicious publish, leaving the compromised release as the only version Cargo would not warn about, according to the report filed to the RustSec advisory database by the researcher who hit it.
• On Windows it writes a PowerShell script to %TEMP% and launches it hidden through a VBScript launcher under wscript.
• 9, all published from the same owner account on August 20, 2026, and all removed within 86 to 107 minutes.

The Rust Project has deleted malicious versions of three widely used Rust crates from crates.

io after a compromised maintainer account published releases that added a typosquatted dependency whose build script downloaded and executed a remote payload during compilation.

The affected releases are arrayref 0.

10, internment 0.

7, and append-only-vec 0.

9, all published from the same owner account on August 20, 2026, and all removed within 86 to 107 minutes.

Because the malicious code sat in the build script of the injected dependency, building a project that resolved it was sufficient to run the payload, and nothing from the crates themselves had to be called.

Developers are advised to search ~/.

cargo/registry/cache for the deleted crate files and to pin arrayref at 0.

9 or earlier, after the Rust Security Response Team unyanked the maliciously-yanked versions during the response.

There is no patched version, no CVE identifier has been assigned, and the RustSec advisories for all three crates record no evidence that any malicious version was used.

"A new version of the arrayref crate was published with a direct dependency on proc-macro1, which would execute a malicious build script.

This compromised version was published on 2026-08-20 and removed approximately 86 minutes later, with no evidence of actual usage," RUSTSEC-2026-0260 said.

The Hacker News has reached out to the Rust Security Response Team for the basis of that finding and for the download count of the deleted versions, but had not received a response at the time of writing.

The Rust Security Response Team said it received the report that the proc-macro1 crate was malicious at 07:15 UTC on August 20 and verified that the crate carried a build script downloading a malicious payload, in an advisory post crediting the Research Team at Nextron Systems GmbH with initially discovering and reporting it.

"We do not believe the author of arrayref to be acting maliciously, but their computer or credentials are likely compromised, and we are attempting to contact them," the Rust Security Response Team said.

The Hacker News confirmed via the crates.

io API on August 21 that the sole listed owner of arrayref is user 2402, David Roundy, registered in October 2009.

How the account was compromised has not been disclosed.

The Rust Security Response Team listed the malicious versions it deleted, with the time each was online -

• arrayref@0.3.10: published at 2026-08-20T07:15:00Z, deleted at 08:41:40Z. Online for 86 minutes.
• internment@0.8.7: published at 07:34:07Z, deleted at 09:04:11Z. Online for 90 minutes.
• append-only-vec@0.1.9: published at 07:37:49Z, deleted at 09:25:24Z. Online for 107 minutes.
• proc-macro1, proc-macro-en, aovine, arone, aronenao, and tinymember, any versions.

Each compromised release carried a single added line in its manifest, a dependency on proc-macro1, a typosquat of the ubiquitous proc-macro2 crate. The library source of proc-macro1 is a genuine copy of proc-macro2, so builds completed normally.

Originally reported by The Hacker News. TechVeb news desk.