CVE-2025-67500: Mastodon is a free, open-source social network server based on ActivityPub. Versions 4.2.27 and prior, 4.3.0-beta.1…
CVE-2025-67500 · Severity: low · CVSS 3.7 · Published 2025-12-10
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.
No. Junglewise Threat Intelligence has no report of CVE-2025-67500 being exploited in the wild.
How severe is CVE-2025-67500?
Low severity, with a CVSS score of 3.7, published 10 December 2025.
Which products and versions are affected?
Joinmastodon Mastodon. The advisory does not name versions.
Is there a fix for CVE-2025-67500?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
Am I affected by CVE-2025-67500?
Check whether you run Joinmastodon Mastodon. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.