CVE-2026-33868: medium-severity vulnerability in mastodon
Mastodon has a GET-Based Open Redirect via '/web/%2F<domain>'
Published · Updated
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
28Vexday Risk Score
Patch soon. It has a working public exploit.
ssvc Attendcvss 4.3epss 0.5%
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
Affected products
mastodon · mastodonRelated CVEs — mastodon
In the same product, most dangerous first.
CVE-2023-36460CRITICALMastodon vulnerable to arbitrary file creation through media attachmentsEPSS 40.1%CVE-2024-23832CRITICALMastodon Remote user impersonation and takeoverEPSS 2.5%CVE-2023-36461HIGHMastodon vulnerable to Denial of Service through slow HTTP responsesEPSS 1.3%CVE-2023-28853HIGHMastodon's blind LDAP injection in login allows the attacker to leak arbitrary attributes from LDAP databaseEPSS 1.3%CVE-2023-36459CRITICALMastodon vulnerable to Cross-site Scripting through oEmbed preview cardsEPSS 1.2%CVE-2026-72916MEDIUMMastodon: SSRF Protection Bypass via IPv4-compatible IPv6 AddressesEPSS 1.0%