Description

The append-only-vec crate 0.1.9 for Rust can trigger execution of malicious code when compiling a project that uses the crate, because it has a rogue dependency that registers with a command-and-control server to offer arbitrary code execution.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.8",
  "pubDate": "2026-08-21T01:17:01.993Z",
  "pubdate": "2026-08-21T01:17:01.993Z",
  "executiveSummary": "The append-only-vec crate version 0.1.9 for Rust suffers from a supply chain vulnerability involving a rogue dependency designed to compromise the build environment. The vulnerability type is classified as malicious code execution via dependency injection, leading to arbitrary code execution on developer systems or compilation servers. The affected product is the append-only-vec crate, specifically version 0.1.9. The risk implications are severe, as unauthorized third-party actors gain the ability to execute arbitrary commands within the context of the user or system compiling the Rust project. Attacker capabilities include registering compromised build environments with a command-and-control (C2) server, enabling continuous remote access, data exfiltration, or further lateral movement into internal development networks. Exploitation requirements are minimal, as the malicious behavior is automatically triggered during the standard compilation lifecycle of any project incorporating the affected crate. No specialized privileges or prior authentication are required by the attacker, since the malicious payload executes inherently as part of build-time script evaluation or dependency resolution mechanisms.",
  "technicalDetails": "The root cause of this vulnerability lies in the inclusion of a malicious, untrusted dependency within the dependency tree of the append-only-vec crate version 0.1.9. In the Rust ecosystem, dependencies specified in Cargo.toml can execute build scripts (build.rs) or procedural macros during the compilation phase, inheriting the permissions and environment of the compiling user. The vulnerable component is the supply chain configuration of the target crate, which incorporates a rogue package explicitly crafted for malicious activity.\nThe exploitation method leverages the package build lifecycle. When a developer or automated CI/CD pipeline compiles a project referencing the affected append-only-vec version, the Rust package manager, Cargo, downloads and compiles the dependency tree. During this compilation phase, the rogue dependency executes its embedded payload without requiring explicit runtime invocation by the primary application code.\nThe attack flow proceeds as follows: First, the target project declares a dependency on the vulnerable append-only-vec 0.1.9 crate. Second, during the cargo build or cargo fetch process, Cargo retrieves the package along with its malicious transitive or direct dependency. Third, the build script or initialization routine of the rogue dependency executes automatically within the local host environment. Fourth, the executing payload establishes outbound network communication, contacting an external command-and-control (C2) server to register the newly infected build environment. Finally, the C2 server receives the check-in and can issue subsequent arbitrary commands for remote code execution.\nThe network exposure is outbound, leveraging standard internet protocols to communicate with attacker-controlled infrastructure, bypassing typical inbound firewall configurations. Authentication and privilege requirements are absent from the attacker's perspective; the code executes with the privileges of the local user running the cargo command, which may include access to sensitive environment variables, SSH keys, cloud credentials, and source code repositories. The post-exploitation impact includes full system compromise of the build host, potential contamination of compiled artifacts with malicious binaries, credential theft, and persistent unauthorized access to the development infrastructure."
}