Description
Mastodon is a free, open-source social network server based on ActivityPub. From 4.3.0 until 4.5.11 and 4.4.18, Mastodon has a feature to let websites credit authors of their articles. To prevent false attribution claims, Mastodon uses the attributionDomains JSON-LD term, however, an error in how it is defined makes Linked Data Signatures on the toot:attributionDomains property ineffective. An attacker can arbitrarily modify the attributionDomains value of a legitimately signed Update activity and bypass Mastodon’s signature verification. This vulnerability is fixed in 4.5.11 and 4.4.18.
References (2)
Core 2
Core References
X_Refsource_Confirm x_refsource_confirm
https://github.com/mastodon/mastodon/security/advisories/GHSA-rwcw-vq68-g34p
Scores
CVSS v3
5.3
EPSS
0.0013
EPSS Percentile
2.9%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
yes
Technical Impact
partial
Details
CWE
CWE-354
Status
published
Products (2)
mastodon/mastodon
>= 4.3.0, < 4.4.18
mastodon/mastodon
>= 4.5.0-beta.1, < 4.5.11
Published
Jun 24, 2026
Tracked Since
Jun 25, 2026