CVE-2026-50128
Mastodon: Spoofing of attribution domains
- State
- Published
- Severity
- 5.3 Medium
- Published
- Jun 24, 2026
- Updated
- Jun 25, 2026
- Reserved
- Jun 3, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 5.3 Medium | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N | GitHub_M |
Weaknesses
- CWE-354 Improper Validation of Integrity Check Value
Affected Products
| Product | Versions |
|---|---|
mastodonmastodon |
|
References
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