TI-2025-20014 Aliases CVE-2025-27157

Mastodon's rate-limits are missing on `/auth/setup`

LOW 30CWE-770Published 2025-02-27 · Updated 2025-02-27

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · Low
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-770.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00369 30th percentileScored 2026-11-07

Fix Fixed mastodon (mastodon): 4.2.16, 4.3.4

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
mastodon	mastodon	4.2.0 to before 4.2.16; 4.3.0 to before 4.3.4	4.2.16, 4.3.4	Patch available	CNA

mastodon Vendormastodon Affected 4.2.0 to before 4.2.16; 4.3.0 to before 4.3.4 Fixed in 4.2.16, 4.3.4 Patch available CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:joinmastodon:mastodon::::::::	4.2.0 to before 4.2.16; 4.3.0 to before 4.3.4	Vulnerable	mastodon

cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:* Versions 4.2.0 to before 4.2.16; 4.3.0 to before 4.3.4 Vulnerable ·mastodon

Remediation

Fix · CNA mastodon (mastodon) Fixed in 4.2.16, 4.3.4

Timeline

2026-10-02 Threatist record created from CVE-2025-27157

References

Patch 1

https://github.com/mastodon/mastodon/commit/06f879ce9bea195344ac9f71e6799eea500628ec

Advisory 1

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

TI-2022-02004 Improper Restriction of Excessive Authentication Attempts in mastodon/mastodon CVSS 3.1CRITICAL 9.8
TI-2025-34613 Mastodon e‑mail throttle misconfiguration allows unlimited email confirmations against unconfirmed emails CVSS 3.1HIGH 7.5
TI-2022-22936 Mastodon through 4.0.2 allows attackers to cause a denial of service (large Sidekiq pull… CVSS 3.1HIGH 7.5
TI-2023-18301 Mastodon vulnerable to arbitrary file creation through media attachments CVSS 3.1CRITICAL 10.0
TI-2023-13359 Mastodon's blind LDAP injection in login allows the attacker to leak arbitrary attributes from LDAP database CVSS 3.1HIGH 7.7
TI-2024-16846 External OpenID Connect Account Takeover by E-Mail Change in mastodon CVSS 3.1HIGH 7.4

See all 41 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences