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Advisory record · RUSTSEC-2026-0265

`proc-macro1` was removed from crates.io due to malicious code

No CVSS score

Published by OSV at 20 Aug 2026, 12:00 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
proc-macro1crates.io>=0.0.0-0No fixed version yet
Identifiers
RUSTSEC-2026-0265
Published
20 Aug 2026
Updated
21 Aug 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

The proc-macro1 crate on crates.io, all versions, was removed for containing a build script that downloads a malicious payload. The source says it was used in a campaign targeting users of arrayref, and gives no details on what the payload does. No fix is listed; users who depend on proc-macro1 should remove it from their projects.

Written 8 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

No source has published a CVSS score for this record yet.

  • CISA KEV Not listed.
  • EPSS No score.

Timeline

  1. 31 Oct 2026, 15:18 UTC First seen by agentprime
  2. 31 Oct 2026, 15:18 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.