Mastodon is a self-hosted, federated microblogging platform. Starting in version 4.2.0 and prior to versions 4.2.16 and 4.3.4, the rate limits are missing on `/auth/setup`. Without those rate limits, an attacker can craft requests that will send an email to an arbitrary addresses. Versions 4.2.16 and 4.3.4 fix the issue.
CVE ID: CVE-2025-27157
CVSS Base Severity: MEDIUM
CVSS Base Score: 5.3
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Vendor: mastodon
Product: mastodon
EPSS Score: 0.05% (probability of being exploited)
EPSS Percentile: 13.61% (scored less or equal to compared to others)
EPSS Date: 2025-03-28 (when was this score calculated)