Cross-site scripting in Mastodon - #VU126981
Published: April 23, 2026
Vulnerability identifier: #VU126981
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U/U:Green
CVE-ID: N/A
CWE-ID: CWE-79
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Mastodon
Affected software:
Mastodon
Mastodon
Detailed vulnerability description
The vulnerability allows a remote attacker to conduct cross-site scripting attacks.
The vulnerability exists due to improper neutralization of input during web page generation in user-facing URLs for remote accounts, posts, and media attachments when handling remote object data. A remote attacker can supply a crafted user-facing URL to conduct cross-site scripting attacks.
Exploitation is limited to third-party clients and servers that strip the Content-Security-Policy header.
Remediation
Install security update from vendor's website.