CVE-2025-27157: mastodon DoS — Fix

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.

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CVSS v3.1 Score

5.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Weakness Type (CWE)

CWE-770 CWE-770

Affected Products

Vendor	Product	Versions
joinmastodon	mastodon	4.2.0 — 4.2.16
joinmastodon	mastodon	4.3.0 — 4.3.4

References

Advisories & Patches

https://github.com/mastodon/mastodon/commit/06f879ce9bea195344ac9f71e6799eea500628ec https://github.com/mastodon/mastodon/security/advisories/GHSA-v39f-c9jj-8w7h

Frequently Asked Questions

What is CVE-2025-27157? +

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. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2025-27157? +

CVE-2025-27157 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-27157? +

CVE-2025-27157 affects products from joinmastodon, specifically: mastodon. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-27157? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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