CVE-2025-27157Network attack vector

Email flooding via unthrottled setup requests

Published Feb 27, 2025 · Updated Feb 27, 2025

Resource exhaustion in Mastodon 4.2.0 through 4.2.15 and 4.3.0 through 4.3.3 allows remote attackers to send arbitrary emails. The PUT and PATCH handlers for /auth/setup accept repeated sign-up email changes without Rack::Attack limits keyed by IP address, destination email, or account. No established account or user interaction is required; repeated requests trigger outbound verification mail and consume mail-delivery resources.

CVSS severity5.3
Medium
EPSS probability0.36%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Mastodon 4.2.0 through 4.2.15 and 4.3.0 through 4.3.3 allows remote attackers to send arbitrary emails. The PUT and PATCH handlers for /auth/setup accept repeated sign-up email changes without Rack::Attack limits keyed by IP address, destination email, or account. No established account or user interaction is required; repeated requests trigger outbound verification mail and consume mail-delivery resources.

The record

CVE
CVE-2025-27157
Published
Feb 27, 2025
Updated
Feb 27, 2025
Vendor
Mastodon
Product
Mastodon
Classifications
CWE-770, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 27, 2025CVE publishedPublication date reported by the CVE source.
  2. Feb 27, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 4.2.0, < 4.2.16
  2. Affected versionversion=>= 4.3.0, < 4.3.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mastodon · Mastodonversion=>= 4.2.0, < 4.2.16; version=>= 4.3.0, < 4.3.4

Published CVSS scores

5.3MastodonCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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