proc-macro-en is a malicious crate published to crates.io as part of the coordinated build-time payload campaign on 2026-08-20 that trojanized arrayref, internment, and append-only-vec and published the proc-macro1 typosquat of proc-macro2. It was used as an attacker-controlled dependency carrying a build-script payload; building it results in the download and execution of a remote binary from https://23.254.165.112:9089/ with 23.254.165.112:443 as command and control. All versions have been removed from crates.io. The individual build script of this crate was not analyzed directly; its behavior is attributed from the campaign.

Credit: OpenSSF (source)

References

• rustsec/advisory-db#3161
• https://github.com/ossf/malicious-packages/blob/65e79a7e3677a36fcdbd109ea6e294bffc77f7db/osv/malicious/crates.io/proc_macro_en/MAL-2026-14339.json
• https://safedep.io/arrayref-proc-macro1-rust-build-time-malware