Which versions of proc-macro1 are malicious?

Every published version of proc-macro1 on crates.io is considered malicious. Remove the package entirely.

How do I remediate proc-macro1 if I installed it?

proc-macro1 establishes remote access, so treat any host that installed it as fully compromised. Isolate the machine, remove the package, rotate all credentials it could reach, and rebuild from a trusted image rather than cleaning in place — a backdoor may have planted additional persistence.

I already installed proc-macro1 — how do I know if it already compromised me?

If proc-macro1 was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.

How do I find proc-macro1 across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for proc-macro1 (all published versions).

Malicious package

proc-macro1crates.io

Advisory published Aug 20, 2026Updated Aug 21, 2026

proc-macro1 is a confirmed malicious crates.io package (MAL-2026-14338) that opens a backdoor for remote access. Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in proc_macro1 (crates.io)

MAL-2026-14338

Immediate action

Remove the package, then rotate any secrets the build/runtime could reach.

remove proc-macro1

What this malware does

proc-macro1 is a typosquat of proc-macro2 published to crates.io by the account 'dtolney', impersonating David Tolnay (dtolnay). Its metadata forges authors 'David Tolnay [email protected]' and points repository at a nonexistent github.com/dtolnay/proc-macro1. The library source is a copy of proc-macro2 so dependent builds succeed, but build.rs reconstructs a base64-encoded URL and downloads an architecture-specific remote binary from https://23.254.165.112:9089/ over TLS with certificate validation disabled (a custom verifier that accepts any certificate), then executes it detached, passing 23.254.165.112:443 as argv[1] (command and control). On Unix it writes and runs /tmp/rust-setup; on Windows it writes %TEMP%\rust-setup.ps1 and launches it via a %TEMP%\rust-setup-launch.vbs launcher under wscript.exe. The download and execution run unconditionally on every build on a supported platform. This crate was the payload carrier pulled in by the trojanized arrayref 0.3.10 release. All versions have been removed from crates.io.

Malicious versions

all versions

Every published version of this package is considered malicious — remove it entirely.

Detection & response playbook

Backdoor / remote access

Find it
Search your lockfiles and build artifacts for proc-macro1 (all published versions).
If you installed it — respond
proc-macro1 establishes remote access, so treat any host that installed it as fully compromised. Isolate the machine, remove the package, rotate all credentials it could reach, and rebuild from a trusted image rather than cleaning in place — a backdoor may have planted additional persistence.
Did it already run?
If proc-macro1 was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.

Frequently asked questions

No. proc-macro1 on crates.io has been identified as a malicious package (all published versions flagged). It should be removed immediately — do not install or keep it in your dependency tree.

References

Credits

SafeDep · finder
jhobern · reporter

Detect & block this

O3 blocks proc-macro1-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the C2 callback and severs the channel.

Malware detection Runtime egress monitoring

Explore

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