Mastodon up to 4.2.27/4.3.14/4.4.9/4.5.2 response discrepancy

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Mastodon up to 4.2.27/4.3.14/4.4.9/4.5.2. This vulnerability affects unknown code. The manipulation leads to response discrepancy. This vulnerability is referenced as CVE-2025-67500. Remote exploitation of the attack is possible. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Mastodon up to 4.2.27/4.3.14/4.4.9/4.5.2 and classified as problematic. This issue affects an unknown functionality. The manipulation with an unknown input leads to a response discrepancy vulnerability. Using CWE to declare the problem leads to CWE-204. The product provides different responses to incoming requests in a way that reveals internal state information to an unauthorized actor outside of the intended control sphere. Impacted is confidentiality. The summary by CVE is:

Mastodon is a free, open-source social network server based on ActivityPub. Versions 4.2.27 and prior, 4.3.0-beta.1 through 4.3.14, 4.4.0-beta.1 through 4.4.9, 4.5.0-beta.1 through 4.5.2 have discrepancies in error handling which allow checking whether a given status exists by sending a request with a non-English Accept-Language header. Using this behavior, an attacker who knows the identifier of a particular status they are not allowed to see can confirm whether this status exists or not. This cannot be used to learn the contents of the status or any other property besides its existence. This issue is fixed in versions 4.2.28, 4.3.15, 4.4.10 and 4.5.3.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2025-67500 since 12/08/2025. The exploitation is known to be difficult. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1592 for this issue.

Upgrading to version 4.2.28, 4.3.15, 4.4.10 or 4.5.3 eliminates this vulnerability. Applying a patch 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

• 4.2.0
• 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
• 4.2.16
• 4.2.17
• 4.2.18
• 4.2.19
• 4.2.20
• 4.2.21
• 4.2.22
• 4.2.23
• 4.2.24
• 4.2.25
• 4.2.26
• 4.2.27
• 4.3.0
• 4.3.1
• 4.3.2
• 4.3.3
• 4.3.4
• 4.3.5
• 4.3.6
• 4.3.7
• 4.3.8
• 4.3.9
• 4.3.10
• 4.3.11
• 4.3.12
• 4.3.13
• 4.3.14
• 4.4.0
• 4.4.1
• 4.4.2
• 4.4.3
• 4.4.4
• 4.4.5
• 4.4.6
• 4.4.7
• 4.4.8
• 4.4.9
• 4.5.0
• 4.5.1
• 4.5.2

Website

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

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