proc-macro1crates.io
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)
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
Every published version of this package is considered malicious — remove it entirely.
Detection & response playbook
Backdoor / remote accessFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for proc-macro1 (all published versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging proc-macro1 across your stack and pipelines.
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 ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.
How O3 protects you
O3 blocks proc-macro1 before install through its supply-chain scanner, and if it has already run, detects and severs the exfiltration or C2 callback at runtime through L7 egress monitoring and eBPF.
Frequently asked questions
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.