What’s Vulnerable › Vulnerabilities
CVE-2026-46349: Mastodon: LD-Signature Bypass via JSON-LD Named-Graph Restructuring
- Severity: medium (CVSS 5.3 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.2% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-06-24 · updated 2026-06-25
- Weakness: CWE-347
Description
Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.5.10, 4.4.17, and 4.3.23, Mastodon's normalization of incoming activities signed with Linked-Data Signatures does not sufficiently protect the activities from a certain class of spoofing, allowing attackers to re-arrange a valid signed JSON-LD activity from a third-party actor to have it processed differently. This vulnerability is fixed in 4.5.10, 4.4.17, and 4.3.23.
Affected products
- mastodon: from 4.5.0-beta.1, < 4.5.10
References
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