CVE-2026-46349 Mastodon: LD-Signature Bypass via JSON-LD Named-Graph Restructuring
Attackers can spoof signed activities by restructuring JSON-LD graphs, bypassing Linked-Data Signature verification in Mastodon.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-46349?
CVE-2026-46349 is a medium-severity vulnerability in mastodon, published on 24 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-347
Which versions are affected by CVE-2026-46349?
1 open source package ship an affected version, including mastodon.
| Package | Affected | Fixed in |
|---|---|---|
mastodon Bitnami | From 4.5.0 | 4.5.10 |
How do I fix CVE-2026-46349?
Upgrade mastodon to 4.5.10 or later.
Is CVE-2026-46349 being exploited?
There is no known exploitation of CVE-2026-46349 in the wild and no public exploit code.
Sources
Also known as BIT-mastodon-2026-46349, GHSA-chgx-jx3p-rf73.