High [CVE-2026-70463] Authorization bypass via `auth users` directive parsing

rsync 3.1.0 before 3.5.0 contains an authorization bypass in auth users directive parsing. The auth users parser uses comma-only tokenization when splitting the user list, which fails to correctly handle entries of the form @Group Name where the group name contains a space.

The space within the group name causes the parser to split the entry at the space boundary, discarding the deny rule associated with the group. An authenticated user whose username or group membership would be denied by an @Group Name auth users entry can connect to a restricted module because the deny rule is silently discarded during parsing.

An authorization bypass flaw was found in the rsync daemon. The auth users directive parser incorrectly handles group names containing spaces due to comma-only tokenization.

This flaw causes deny rules to be silently discarded, allowing an authenticated user to bypass restrictions and gain unauthorized access to restricted modules. The flaw allows an authenticated, but unauthorized, user to access restricted rsync modules due to incorrect parsing of deny rules.

This bypass occurs because the rsync parser fails to properly tokenize group names with embedded spaces, silently discarding intended access restrictions. Red Hat severity: Important — CVSS 8.1 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N).

Weakness: CWE-863.