CVE-2026-48028
Mastodon: Removal of integrity-protected JSON entries from signed activities
6.5
MEDIUM
CVSS 3.1
EPSS 0.12%
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 threat actors to remove JSON entries from valid signed activities from a third-party actor. This vulnerability is fixed in 4.5.10, 4.4.17, and 4.3.23.
How to fix CVE-2026-48028
To remediate CVE-2026-48028, upgrade the affected package to a fixed version below.
- —upgrade to 4.3.23 or later
Is CVE-2026-48028 being exploited?
Low — EPSS is 0.1%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- from 0, < 4.3.23, >= 4.4.0, < 4.4.17, >= 4.5.0, < 4.5.10
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L |