CVE-2026-33868: Mastodon has a GET-Based Open Redirect via '/web/%2F<domain>'
Affected: mastodon · Exploitation: check available, not yet exploited
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 42% of scored CVEs
DescriptionCVE.org
Mastodon is a free, open-source social network server based on ActivityPub. Prior to versions 4.5.8, 4.4.15, and 4.3.21, an unauthenticated Open Redirect vulnerability (CWE-601) exists in the `/web/*` route due to improper handling of URL-encoded path segments. An attacker can craft a specially encoded URL that causes the application to redirect users to an arbitrary external domain, enabling phishing attacks and potential OAuth credential theft. The issue occurs because URL-encoded slashes (`%2F`) bypass Rails path normalization and are interpreted as host-relative redirects. Versions 4.5.8, 4.4.15, and 4.3.21 patch the issue.
Affected products1
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- mastodon · mastodon>= 4.5.0, < 4.5.8; >= 4.4.0, < 4.4.15; < 4.3.21
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Check available, not yet exploited. A public nuclei template can confirm it on a system you are authorised to test.
- CISA KEV
- Not listed
- Public check
- Mastodon - Open Redirect · nuclei template in projectdiscovery/nuclei-templates
- Weakness
- Open Redirect
- Vendor
- mastodon
- Published
- March 2026
CoverageNo articles yet
No CyberSIXT article names CVE-2026-33868 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.