Mastodon up to 4.1.22/4.2.15/4.3.3 information disclosure

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Mastodon up to 4.1.22/4.2.15/4.3.3. Affected is an unknown function. Performing a manipulation results in information disclosure. This vulnerability is cataloged as CVE-2025-27399. It is possible to initiate the attack remotely. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Mastodon up to 4.1.22/4.2.15/4.3.3. It has been classified as problematic. This affects an unknown functionality. The manipulation with an unknown input leads to a information disclosure vulnerability. CWE is classifying the issue as CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. This is going to have an impact on confidentiality. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2025-27399 since 02/24/2025. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1592 according to MITRE ATT&CK.

Upgrading to version 4.1.23, 4.2.16 or 4.3.4 eliminates this vulnerability. Applying the patch 6b519cfefa93a923b19d0f20c292c7185f8fd5f5 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Name

• Mastodon

Version

• 4.1.0
• 4.1.1
• 4.1.2
• 4.1.3
• 4.1.4
• 4.1.5
• 4.1.6
• 4.1.7
• 4.1.8
• 4.1.9
• 4.1.10
• 4.1.11
• 4.1.12
• 4.1.13
• 4.1.14
• 4.1.15
• 4.1.16
• 4.1.17
• 4.1.18
• 4.1.19
• 4.1.20
• 4.1.21
• 4.1.22
• 4.2.0
• 4.2.1
• 4.2.2
• 4.2.3
• 4.2.4
• 4.2.5
• 4.2.6
• 4.2.7
• 4.2.8
• 4.2.9
• 4.2.10
• 4.2.11
• 4.2.12
• 4.2.13
• 4.2.14
• 4.2.15
• 4.3.0
• 4.3.1
• 4.3.2
• 4.3.3

License

• open-source

Website

• Product: https://github.com/mastodon/mastodon/

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