CVE-2025-54879
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.54%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 0.54% probability · 44th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-770
- Affected
- joinmastodon/mastodon
- Source
- security-advisories@github.com
References
- https://github.com/mastodon/mastodon/commit/e2592419d93fb41be03c2f3ff6a122fecb0e0952Patch
- https://github.com/mastodon/mastodon/releases/tag/v4.4.3Release Notes
- https://github.com/mastodon/mastodon/security/advisories/GHSA-84ch-6436-c7mgThird Party Advisory
- https://github.com/mastodon/mastodon/security/advisories/GHSA-84ch-6436-c7mgThird Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.