CVE-2026-48028 Mastodon: Removal of integrity-protected JSON entries from signed activities
Attackers can remove JSON entries from valid signed activities in Mastodon, enabling spoofing and data modification.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-48028?
CVE-2026-48028 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 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.
Weakness: CWE-354
Which versions are affected by CVE-2026-48028?
1 open source package ship an affected version, including mastodon.
| Package | Affected | Fixed in |
|---|---|---|
mastodon Bitnami | All versions | 4.3.23, 4.4.17, 4.5.10 |
How do I fix CVE-2026-48028?
Upgrade mastodon to a fixed version for your release line: 4.3.23, 4.4.17 or 4.5.10.
Is CVE-2026-48028 being exploited?
There is no known exploitation of CVE-2026-48028 in the wild and no public exploit code.
Sources
Also known as BIT-mastodon-2026-48028, GHSA-53m7-2wrh-q839.