CVE-2026-46349CWE-347

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

Medium · published June 24, 2026

CVSS v3.1
5.3
EPSS
0%
Percentile
8.7
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
5.3 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00195 · 8.7th percentile
Weakness
CWE-347 · Improper Verification of Cryptographic Signature
Published
2026-06-24T19:40Z
EPSS history
Timeline
  • 24 JUN 19:40Z
    Mastodon: LD-Signature Bypass via JSON-LD Named-Graph Restructuring
    cvelistv5