CVE-2026-5222: Cargo can be coerced to share credentials between registries

The Rust Security Response Team was notified that Cargo incorrectly normalized the URLs of third-party registries using the [sparse index protocol][1]. If a hosting provider allowed multiple registries to be hosted with arbitrary names within the same domain, an attacker able to publish crates in a registry could obtain the credentials of others users of the same registry.

This vulnerability is tracked as CVE-2026-5222. The severity of the vulnerability is low, due to the extremely niche requirements needed to achieve the attack.