Mastodon: LD-Signature Bypass via JSON-LD Named-Graph Restructuring

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.

Scores

EPSS (exploitation in 30 days)

0.19% · top 91% of all CVEs (6 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: yes · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.3.

Weakness

• CWE-347: Improper Verification of Cryptographic Signature (opens in a new tab)All about CWE-347 and its CVEs

Affected products

• mastodon · mastodon

  • affected >= 4.5.0-beta.1, < 4.5.10

References (1)

• https://github.com/mastodon/mastodon/security/advisories/GHSA-chgx-jx3p-rf73 (opens in a new tab)x_refsource_CONFIRM

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-46349](https://trackcve.app/badge/CVE-2026-46349.svg)](https://trackcve.app/cve/CVE-2026-46349)

Record last updated 25 Jun 2026, 13:16 UTC.