# CVE-2026-77651: arrayref crate malicious dependency code execution at build time

Source: https://junglewise.ai/threats/cve-2026-77651-arrayref-crate-malicious-dependency-code-execution-at-build-time  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-21. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-77651 · Severity: critical · CVSS 9.8 · Published 2026-08-21

The arrayref Rust library, a widely-used utility crate for array operations, was compromised to include a malicious dependency that downloads and executes arbitrary code during the build process. Developers who built projects using the affected version would unknowingly execute a remote payload, potentially compromising their development machines and entire build environments with arbitrary code execution capabilities.

Technologies: [append-only-vec (crates.io)](https://junglewise.ai/threats/technologies/append-only-vec), [arrayref (crates.io)](https://junglewise.ai/threats/technologies/arrayref), [internment (crates.io)](https://junglewise.ai/threats/technologies/internment), [proc-macro1 (crates.io)](https://junglewise.ai/threats/technologies/proc-macro1). Vendors: [crates.io](https://junglewise.ai/threats/vendors/crates-io).

## Quick answers

**Is CVE-2026-77651 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-77651 being exploited in the wild.

**How severe is CVE-2026-77651?** Critical severity, with a CVSS score of 9.8, published 21 August 2026.

**Which products and versions are affected?** append-only-vec (crates.io) 0.1.9; arrayref (crates.io) 0.3.10; internment (crates.io) 0.8.7; proc-macro1 (crates.io) 1.0.107.

**Is there a fix for CVE-2026-77651?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-77651 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-77651?** Check whether you run append-only-vec (crates.io), arrayref (crates.io), internment (crates.io) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A supply chain attack compromised the arrayref crate (v0.3.10) by introducing a malicious dependency on a typosquatted proc-macro1 crate. The attacker's proc-macro1 build script downloads and executes a remote binary from 23.254.165.112:9089, with no certificate validation (AcceptAll verifier). The payload runs during compilation with context-specific executables (Linux: /tmp/rust-setup, Windows: PowerShell via VBS launcher) that spawn detached processes and communicate with a command-and-control server. The attack leverages yanked previous versions (0.3.5–0.3.9) to lure developers to upgrade to the malicious 0.3.10. Patches are not applicable; the malicious versions were deleted from crates.io on 2026-08-20, and the crate maintainer's account was locked.

## Affected products

- Rust arrayref 0.3.10
- Rust proc-macro1 1.0.107
- Rust internment 0.8.7
- Rust append-only-vec 0.1.9

## Timeline

- 2026-08-20: disclosed: Rust Security Response Team notified of proc-macro1 malice; malicious arrayref 0.3.10 published 07:15 UTC
- 2026-08-20: other: arrayref 0.3.10 deleted after 86 minutes online
- 2026-08-20: other: append-only-vec 0.1.9 deleted after 107 minutes online
- 2026-08-21: advisory

## References

- [https://blog.rust-lang.org/2026/08/20/supply-chain-attack-on-arrayref](https://blog.rust-lang.org/2026/08/20/supply-chain-attack-on-arrayref)
- [https://github.com/rustsec/advisory-db/issues/3161](https://github.com/rustsec/advisory-db/issues/3161)

## Related threats

- [append-only-vec crate malicious build script supply chain attack](https://junglewise.ai/threats/cve-2026-77650-append-only-vec-crate-malicious-build-script-supply-chain-attack)
- [internment Rust crate malicious dependency injection](https://junglewise.ai/threats/cve-2026-77649-internment-rust-crate-malicious-dependency-injection)
- [RUSTSEC-2026-0265 - `proc-macro1` was removed from crates.io due to malicious code](https://junglewise.ai/threats/rustsec-2026-0265-proc-macro1-was-removed-from-crates-io-due-to-3b17138c)
- [RUSTSEC-2026-0260 - `arrayref` 0.3.10 was removed from crates.io due to a malicious dependency](https://junglewise.ai/threats/rustsec-2026-0260-arrayref-0-3-10-was-removed-from-crates-io-due-to-a-74c1bdae)
- [RUSTSEC-2026-0266 - `internment` 0.8.7 was removed from crates.io due to a malicious dependency](https://junglewise.ai/threats/rustsec-2026-0266-internment-0-8-7-was-removed-from-crates-io-due-to-a-8642dfec)