RUSTSEC-2026-0265 `proc-macro1` was removed from crates.io due to malicious code
A malicious Rust crate named proc-macro1 was published to crates.io, allowing attackers to execute arbitrary code via its build script.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is RUSTSEC-2026-0265?
RUSTSEC-2026-0265 is a vulnerability in proc-macro1, published on 20 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
It was reported proc-macro1 contained a build script that would download a
malicious payload.
This crate had two versions, both published on 2026-08-20. The crate was removed from crates.io and related user accounts were locked.
This crate was used as part of a malware campaign targeted at users of
arrayref, which was downloaded 2,285 times before being removed; see
the arrayref advisory for more detail.
Thanks to the Research Team at Nextron Systems GmbH for reporting this to the Rust security response working group, and thanks to Emily Albini for coordinating with the crates.io and infra-admin teams.
Which versions are affected by RUSTSEC-2026-0265?
1 open source package ship an affected version, including proc-macro1.
| Package | Affected | Fixed in |
|---|---|---|
proc-macro1 crates.io | From 0.0.0-0 | None |
How do I fix RUSTSEC-2026-0265?
No fix has been published for RUSTSEC-2026-0265 yet. Limit exposure of the affected software until one is available.
Is RUSTSEC-2026-0265 being exploited?
There is no known exploitation of RUSTSEC-2026-0265 in the wild and no public exploit code.