github.comConfirmation
https://github.com/mastodon/mastodon/security/advisories/GHSA-5r37-qpwq-2jhh CVE-2026-41259
HIGH
Mastodon: Insufficient verification of email addresses
Record summary
CVE-2026-41259 has a selected CVSS score of 8.2 (high).
Description
Mastodon is a free, open-source social network server based on ActivityPub. Prior to v4.5.9, v4.4.16, and v4.3.22, Mastodon allows restricting new user sign-up based on e-mail domain names, and performs basic validation on e-mail addresses, but fails to restrict characters that are interpreted differently by some mailing servers. This vulnerability is fixed in v4.5.9, v4.4.16, and v4.3.22.
Description source: CVE List
Exploitation context
CISA SSVC decision
ExploitationNone
AutomatableYes
Technical impactPartial
CISA Coordinator · SSVC 2.0.3 · Evaluated Apr 23, 2026 · Source: CVE List
Affected products and versions
1| Product | Source | Version range | Status |
|---|---|---|---|
mastodonBrowse mastodon / mastodon | CVE List | < 4.3.22 | affected |
| >= 4.4.0-beta.1, < 4.4.16 | affected | ||
| >= 4.5.0-beta.1, < 4.5.9 | affected |