Input validation error in Mastodon - CVE-2026-48028
Published: May 23, 2026
Vulnerability identifier: #VU132183
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-48028
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to selectively hide contents of a signed activity.
The vulnerability exists due to improper input validation in incoming activity normalization for Linked-Data Signatures when processing signed activities from a third-party actor. A remote attacker can remove JSON entries from a valid signed activity to selectively hide contents of a signed activity.
Exploitation requires access to the original signed activity object.
Affected software
Mastodon
How to mitigate CVE-2026-48028
Install security update from vendor's website.
Mastodon - addressed in versions 4.3.23, 4.4.17, 4.5.10