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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
Required
User action required
Impact Assessment
Confidentiality
Low
Partial data leak
Integrity
Low
Partial data modification
Availability
None
No disruption
CVSS Vector v3.1
Weakness Type (CWE)
Vulnerable Products 3
| Configuration | From (including) | Up to (excluding) |
|---|---|---|
|
Joinmastodon Mastodon
cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*
|
— |
4.3.21
|
|
Joinmastodon Mastodon
cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*
|
4.4.0
|
4.4.15
|
|
Joinmastodon Mastodon
cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*
|
4.5.0
|
4.5.8
|