Mail-queue exhaustion via misbound confirmation throttle
Published Aug 5, 2025 · Updated Aug 6, 2025
Rate-limit bypass in Mastodon 3.1.5 through 4.2.23, 4.3.0 through 4.3.10, and 4.4.0 through 4.4.2 allows remote attackers to overload mail queues. The email-confirmation throttle in config/initializers/rack_attack.rb matches /auth/password instead of /auth/confirmation, so confirmation requests never increment the per-address counter. No account is required; rotating source IP addresses evades the remaining IP limit, enabling confirmation-email spam and mail-queue exhaustion.
Summary
What happened
Rate-limit bypass in Mastodon 3.1.5 through 4.2.23, 4.3.0 through 4.3.10, and 4.4.0 through 4.4.2 allows remote attackers to overload mail queues. The email-confirmation throttle in config/initializers/rack_attack.rb matches /auth/password instead of /auth/confirmation, so confirmation requests never increment the per-address counter. No account is required; rotating source IP addresses evades the remaining IP limit, enabling confirmation-email spam and mail-queue exhaustion.
The record
- CVE
- CVE-2025-54879
- Published
- Aug 5, 2025
- Updated
- Aug 6, 2025
- Vendor
- Mastodon
- Product
- Mastodon
- Classifications
- CWE-770, T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 5, 2025CVE publishedPublication date reported by the CVE source.
- Aug 6, 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.
- Affected versionversion=>= 3.1.5, < 4.2.24
- Affected versionversion=>= 4.3.0, < 4.3.11
- Affected versionversion=>= 4.4.0, < 4.4.3
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
- Unauthenticated confirmation-email throttle bypass procedureproof of concept · unverified
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
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