CVE-2026-33868
Last modified
CVE-2026-33868 is a medium-severity vulnerability rated 6.1/10 on the CVSS scale. 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. EPSS estimates a 0.52% chance of exploitation in the next 30 days.
Description
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.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Joinmastodon | Mastodon | < 4.3.21 |
| Joinmastodon | Mastodon | >= 4.4.0, < 4.4.15 |
| Joinmastodon | Mastodon | >= 4.5.0, < 4.5.8 |
References
Timeline
- Published
- Last Modified
- Status
- Analyzed
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