BIT-mastodon-2026-50128: Mastodon: Spoofing of attribution domains
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.
BIT-mastodon-2026-50128: Mastodon: Spoofing of attribution domains
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.
Affected software
pkg:bitnami/mastodonRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- BIT-mastodon-2026-50128
- Osv Schema Version
- 1.6.2
- Aliases
- ["CVE-2026-50128"]
- Ecosystems
- ["Bitnami"]
- Database Specific Severity
- Medium
- Cvss Version
- null
Threat ID: 6a4c347427e9c79719603a93
Added to database: 07/06/2026, 23:04:20 UTC
Last updated: 07/06/2026, 23:04:20 UTC
Views: 1
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