Medium severity · published Jun 24, 2026
CVE-2026-48028
Mastodon: Removal of integrity-protected JSON entries from signed activities
6.5
CVSS
0.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
Low
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 7% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MA
mastodon · mastodon
>= 4.5.0-beta.1, < 4.5.10; >= 4.4.0-beta.1, < 4.4.17; < 4.3.23 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-48028
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-48028
github.com
https://github.com/mastodon/mastodon/security/advisories/GHSA-53m7-2wrh-q839
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