CVE-2026-33868— Mastodon has a GET-Based Open Redirect via '/web/%2F<domain>'
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I. Basic Information for CVE-2026-33868
Vulnerability Information
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Vulnerability Title
Mastodon has a GET-Based Open Redirect via '/web/%2F<domain>'
Source: NVD (National Vulnerability Database)
Vulnerability 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.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
Source: NVD (National Vulnerability Database)
Vulnerability Type
指向未可信站点的URL重定向(开放重定向)
Source: NVD (National Vulnerability Database)
Vulnerability Title
Mastodon 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mastodon是Mastodon开源的一款基于ActivityPub的开源社交网络服务器。 Mastodon 4.5.8之前版本、4.4.15之前版本和4.3.21之前版本存在输入验证错误漏洞，该漏洞源于/web/*路由对URL编码路径段处理不当，可能导致未经验证的重定向和钓鱼攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
II. Public POCs for CVE-2026-33868
| # | POC Description | Source Link | Shenlong Link |
|---|---|---|---|
| 1 | Mastodon version < 4.5.8, < 4.4.15, < 4.3.21 is vulnerable to unauthenticated Open Redirect vulnerability (CWE-601) exists in the /web/* route due to improper handling of URL-encoded path segments. | https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-33868.yaml | POC Details |
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IV. Related Vulnerabilities
Same product: mastodon
- CVE-2026-41259
Mastodon: Insufficient verification of email addresses - CVE-2026-33869
Mastodon has a denial of service for quote authorization - CVE-2026-27477
Mastodon has SSRF via unvalidated FASP Provider base_url - CVE-2026-27468
Mastodon may allow unconfirmed FASP to make subscriptions - CVE-2026-25540
Mastodon's signature-dependent ActivityPub collection respon
Same vendor: mastodon
- CVE-2026-41259
Mastodon: Insufficient verification of email addresses - CVE-2026-33869
Mastodon has a denial of service for quote authorization - CVE-2026-27477
Mastodon has SSRF via unvalidated FASP Provider base_url - CVE-2026-27468
Mastodon may allow unconfirmed FASP to make subscriptions - CVE-2026-25540
Mastodon's signature-dependent ActivityPub collection respon
Same weakness: CWE-601
- CVE-2026-42350
Kargo: Open Redirect in UI OIDC Login Flow via redirectTo Qu - CVE-2026-42195
Unvalidated gitlab URL parameter redirects OAuth authorize s - CVE-2026-3318
Multiple vulnerabilities in Cradle e-commerce - CVE-2026-42259
Saltcorn: Open Redirect in `POST /auth/login` due to incompl - CVE-2026-6795
Open Redirect in DivvyDrive Information Technologies' DivvyD
V. Comments for CVE-2026-33868
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