CVE-2025-27157 Mastodon's rate-limits are missing on `/auth/setup`
Attackers can bypass rate limits on the setup endpoint to spam arbitrary email addresses, causing resource exhaustion and service disruption.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-27157?
CVE-2025-27157 is a medium-severity denial of service vulnerability in mastodon, published on 27 Feb 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-770
Which versions are affected by CVE-2025-27157?
1 open source package ship an affected version, including mastodon. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
mastodon Bitnami | From 4.2.0 | 4.3.4 |
Products include Joinmastodon Mastodon.
How do I fix CVE-2025-27157?
Upgrade mastodon to 4.3.4 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-27157 being exploited?
There is no known exploitation of CVE-2025-27157 in the wild and no public exploit code.
Other vulnerabilities in mastodon
- CVE-2023-36460 Mastodon vulnerable to arbitrary file creation through media attachments
- CVE-2022-2166 Improper Restriction of Excessive Authentication Attempts in mastodon/mastodon
- CVE-2022-24307 Missing authorization in n/a
- CVE-2018-21018 Auth bypass in n/a
- CVE-2024-23832 Mastodon Remote user impersonation and takeover
Sources
Also known as BIT-mastodon-2025-27157, GHSA-v39f-c9jj-8w7h.