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 through 4.3.14, 4.4.0-beta.1 through 4.4.9…

PriorityP416low3.7CVSS 3.1

AVNACHPRNUINSUCLINAN

EPSS

0.19%

8.6th percentile

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.

Affected

8 ranges

Vendor	Product	Version range	Fixed in
joinmastodon	mastodon	< 4.2.28	4.2.28
joinmastodon	mastodon	>= 4.3.0 < 4.3.15	4.3.15
joinmastodon	mastodon	>= 4.4.0 < 4.4.10	4.4.10
joinmastodon	mastodon	>= 4.5.0 < 4.5.3	4.5.3
mastodon	mastodon	< 4.2.28	4.2.28
mastodon	mastodon	—	—
mastodon	mastodon	—	—
mastodon	mastodon	—	—

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