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CVE-2026-33868

Published: Mar 27, 2026Modified: Jun 17, 2026

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6.1
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Exploitability: 2.8 / Impact: 2.7
Source: NVD

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.

Affected (3)

1 product
Mastodon
Configuration A
3 vulnerable
Vulnerable SoftwareAffected Versions
Joinmastodon
Before 4.3.21
From 4.4.0 to 4.4.15
From 4.5.0 to 4.5.8

References (1)

Source: security-advisories@github.com
Vendor Advisory

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