Mastodon's domain blocks & rationales ignore user approval when visibility set as "users"
Priority LOW 30CWE-200Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Information disclosure, Security bypass
- Confidentiality · integrity · availability
- Low · None · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-200 and CWE-285.
Summary
Mastodon is a self-hosted, federated microblogging platform. In versions prior to 4.1.23, 4.2.16, and 4.3.4, when the visibility for domain blocks/reasons is set to "users" (localized English string: "To logged-in users"), users that are not yet approved can view the block reasons. Instance admins that do not want their domain blocks to be public are impacted. Versions 4.1.23, 4.2.16, and 4.3.4 fix the issue.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00357 29th percentileScored 2026-11-07
Fix Fixed mastodon (mastodon): 4.1.23, 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 | before 4.1.23; 4.2.0 to before 4.2.16; 4.3.0 to before 4.3.4 | 4.1.23, 4.2.16, 4.3.4 | Patch available | CNA |
- mastodon Vendormastodon Affected before 4.1.23; 4.2.0 to before 4.2.16; 4.3.0 to before 4.3.4 Fixed in 4.1.23, 4.2.16, 4.3.4 Patch available CNA
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:* | before 4.1.23; 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 before 4.1.23; 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 4.1.23, 4.2.16, 4.3.4
Timeline
- 2026-10-02 Threatist record created from CVE-2025-27399
References
Other 2
- https://github.com/mastodon/mastodon/blob/93f0427b8a84faf68d5d02cdf9a26f98fae16f2b/app/controllers/api/v1/instances/domain_blocks_controller.rb#L33-L35
- https://github.com/mastodon/mastodon/blob/93f0427b8a84faf68d5d02cdf9a26f98fae16f2b/app/controllers/api/v1/instances/domain_blocks_controller.rb#L49-L51
More Mastodon vulnerabilities
- 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
Sources
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences