CVE-2025-54879: mastodon DoS — Fix

Description

Mastodon is a free, open-source social network server based on ActivityPub Mastodon which facilitates LDAP configuration for authentication. In versions 3.1.5 through 4.2.24, 4.3.0 through 4.3.11 and 4.4.0 through 4.4.3, Mastodon's rate-limiting system has a critical configuration error where the email-based throttle for confirmation emails incorrectly checks the password reset path instead of the confirmation path, effectively disabling per-email limits for confirmation requests. This allows attackers to bypass rate limits by rotating IP addresses and send unlimited confirmation emails to any email address, as only a weak IP-based throttle (25 requests per 5 minutes) remains active. The vulnerability enables denial-of-service attacks that can overwhelm mail queues and facilitate user harassment through confirmation email spam. This is fixed in versions 4.2.24, 4.3.11 and 4.4.3.

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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	3.1.5 — 4.2.24
joinmastodon	mastodon	4.3.0 — 4.3.11
joinmastodon	mastodon	4.4.0 — 4.4.3

References

Advisories & Patches

https://github.com/mastodon/mastodon/commit/e2592419d93fb41be03c2f3ff6a122fecb0e0952

Other References

https://github.com/mastodon/mastodon/releases/tag/v4.4.3 https://github.com/mastodon/mastodon/security/advisories/GHSA-84ch-6436-c7mg https://github.com/mastodon/mastodon/security/advisories/GHSA-84ch-6436-c7mg

Frequently Asked Questions

What is CVE-2025-54879? +

Mastodon is a free, open-source social network server based on ActivityPub Mastodon which facilitates LDAP configuration for authentication. In versions 3.1.5 through 4.2.24, 4.3.0 through 4.3.11 and 4.4.0 through 4.4.3, Mastodon's rate-limiting system has a critical configuration error where the email-based throttle for confirmation emails incorrectly checks the password reset path instead of the confirmation path, effectively disabling per-email limits for confirmation requests. This allows attackers to bypass rate limits by rotating IP addresses and send unlimited confirmation emails to any email address, as only a weak IP-based throttle (25 requests per 5 minutes) remains active. The vulnerability enables denial-of-service attacks that can overwhelm mail queues and facilitate user harassment through confirmation email spam. This is fixed in versions 4.2.24, 4.3.11 and 4.4.3. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2025-54879? +

CVE-2025-54879 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-2025-54879? +

CVE-2025-54879 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-2025-54879? +

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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