Arti 2.5 brings stable Counter Galois Onion, default Congestion Control and security fixes

Arti, the Tor Project’s next-generation Tor implementation in Rust, has been updated to version 2.5. This release delivers several improvements focused on security, speed, and future capabilities.

The Counter Galois Onion encryption method, designed to improve privacy for Tor circuit traffic, is now marked as stable and included in full feature builds of Arti. Alongside this, Congestion Control is enabled by default, allowing users to benefit from increased network speeds without requiring extra configuration.

On the security front, two medium-severity denial-of-service (DoS) vulnerabilities, labeled TROVE-2026-024 and TROVE-2026-027, have been disclosed and fixed as part of this update. Following these changes, the release updates Arti’s minimum supported compiler requirement to Rust version 1.91, which may affect developers using older toolchains.

Building on core Tor functionality, Arti 2.5 continues ongoing development work needed to support operation as a relay and as a directory authority. In addition to major changes, users will also find numerous bug fixes, internal cleanups, and assorted improvements throughout the codebase.