CVE-2026-46349
Mastodon: LD-Signature Bypass via JSON-LD Named-Graph Restructuring
5.3
MEDIUM
CVSS 3.1
EPSS 0.16%
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.
How to fix CVE-2026-46349
To remediate CVE-2026-46349, upgrade the affected package to a fixed version below.
- —upgrade to 4.5.10 or later
Is CVE-2026-46349 being exploited?
Low — EPSS is 0.2%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- >= 4.5.0, < 4.5.10
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N |