# CVE-2026-77650: append-only-vec crate malicious build script supply chain attack

Source: https://junglewise.ai/threats/cve-2026-77650-append-only-vec-crate-malicious-build-script-supply-chain-attack  
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-2026-77650 · Severity: critical · CVSS 9.8 · Published 2026-08-21

The append-only-vec crate, a Rust library used in software projects, was compromised and published with a malicious build script that executes arbitrary code during compilation. When a developer builds a project that depends on the affected version, the malware downloads and runs executable code from an attacker-controlled server, potentially giving the attacker complete control over the developer's machine and any systems they deploy code to.

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-2026-77650 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-77650 being exploited in the wild.

**How severe is CVE-2026-77650?** 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-2026-77650?** A patch was published on 2026-08-20: Malicious versions removed and accounts locked by Rust Security Response Team Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-77650 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-77650?** 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

This is a supply chain attack via dependency injection in the Rust package ecosystem. The compromised append-only-vec 0.1.9 crate depends on a typosquatted rogue crate (proc-macro1) whose build.rs script downloads a malicious binary from 23.254.165.112:9089 and executes it during the build phase with no user interaction required. The payload is delivered as platform-specific executables (ELF on Unix, PowerShell on Windows) that connect to command-and-control servers. The attack affects the build environment of any developer or CI/CD system that compiles code depending on the malicious version. The malicious version was published on 2026-08-20 and remained accessible for 107 minutes before removal by the Rust Security Response Team.

## Affected products

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

## Timeline

- 2026-08-20: disclosed: Malicious versions published to crates.io
- 2026-08-20: other: append-only-vec 0.1.9 published
- 2026-08-20: other: append-only-vec 0.1.9 deleted after 107 minutes online
- 2026-08-20: patched: Malicious versions removed and accounts locked by Rust Security Response Team

## 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

- [arrayref crate malicious dependency code execution at build time](https://junglewise.ai/threats/cve-2026-77651-arrayref-crate-malicious-dependency-code-execution-at-build-time)
- [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)