CVE-2026-46349: Mastodon: LD-Signature Bypass via JSON-LD Named-Graph Restructuring
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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Mastodonto a version that resolves this vulnerability.Fixed in 4.5.10 - Upgrade
Upgrade
Mastodonto a version that resolves this vulnerability.Fixed in 4.4.17 - Upgrade
Upgrade
Mastodonto a version that resolves this vulnerability.Fixed in 4.3.23
Event History
Frequently Asked Questions
What is the severity of CVE-2026-46349?
The severity of CVE-2026-46349 is medium with a score of 5.3.
What is CVE-2026-46349 about?
CVE-2026-46349 involves a LD-Signature Bypass vulnerability in Mastodon that allows attackers to spoof activities signed with Linked-Data Signatures.
How do I fix CVE-2026-46349?
To fix CVE-2026-46349, you should upgrade to Mastodon version 4.5.10, 4.4.17, or 4.3.23 or later.
Is CVE-2026-46349 exploitable by remote attackers?
Yes, CVE-2026-46349 can be exploited by remote attackers due to the nature of the vulnerability.
What versions of Mastodon are vulnerable to CVE-2026-46349?
Mastodon versions prior to 4.5.10, 4.4.17, and 4.3.23 are vulnerable to CVE-2026-46349.