astral-tokio-tar v0.6.0 Flaw Allows Arbitrary Directory Permission Manipulation via Symlinks

A critical security audit has identified a symlink-based vulnerability in the astral-tokio-tar Rust crate (versions 0.6.0 and earlier), allowing attackers to modify permissions on directories outside the intended archive hierarchy. The flaw, catalogued as RUSTSEC-2026-0113, resides in the unpack_in API, which fails to properly validate symlink traversal before executing chmod operations. An attacker who crafts a malicious tar archive could leverage this defect to alter directory permissions on external file system locations—a stealthy vector for privilege escalation or persistence within affected systems. File permissions remain unaffected by this specific flaw. A second related vulnerability, RUSTSEC-2026-0112, involves PAX header desynchronization in the same package versions. Both issues were disclosed on May 3, 2026, with patched versions (>=0.6.1) now available. The astral-tokio-tar crate, an async-compatible tar manipulation library for Rust, is widely used in archive processing, backup tooling, and container-related workflows. Users are advised to audit dependencies for astral-tokio-tar@<=0.6.0 and prioritize immediate updates. The equivalent symlink vulnerability in the foundational tar crate (GHSA-j4xf-2g29-59ph) suggests a systemic issue within Rust's archive handling ecosystem that warrants broader scrutiny across dependent projects.