Nix versions prior to 2.35.3 contain a flaw that, when the daemon runs without sandboxing on macOS or FreeBSD, it incorrectly permits connections initiated by build users. This bypasses the intended privilege restrictions, allowing an attacker to interact with the Nix daemon over the network. The core weakness is a violation of privilege assignment policy, consistent with CWE‑863. Based on the description, it is inferred that the attack vector requires a build user with some privileges and that the attacker can use that to connect to the daemon.

Nix, the package manager maintained by NixOS, is affected in all releases earlier than 2.35.3 when the daemon is configured to run without sandboxing on macOS and FreeBSD platforms. The vulnerability does not affect other operating systems or sandboxed configurations. Users of the default unsandboxed Nix daemon on these platforms should verify their version and upgrade accordingly.

The CVSS score of 4.3 indicates a low severity, and the EPSS value of less than 1% suggests a very low probability of exploitation in the current threat landscape. The vulnerability is not listed in CISA’s KEV catalog, implying no known widespread attacks. Attackers would need local or network access to a build user with privileges to initiate connections to the Nix daemon. Based on the description, it is inferred that the attack vector involves local or network access to that build user. In a typical build environment, such access might be limited, making the practical risk moderate but not negligible.