Open redirect in Mastodon - CVE-2026-33868
Published: April 23, 2026
Vulnerability identifier: #VU126998
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-33868
CWE-ID: CWE-601
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 redirect users to an arbitrary external site.
The vulnerability exists due to url redirection to an untrusted site in the /web/* route when handling specially encoded path segments. A remote attacker can send a specially crafted URL to redirect users to an arbitrary external site.
User interaction is required to follow the crafted link, and the issue involves URL-encoded slashes being interpreted as host-relative redirects.
How to mitigate CVE-2026-33868
Install security update from vendor's website.