CVE-2026-41259
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.
SeverityHigh
CVSS7.5
Exploit probability—
Product
Mastodon
PublishedApr 23, 2026
First seenApr 23, 2026
Weakness typeCWE-841CWE-841
How to fix
Update
- joinmastodon mastodon4.3.22, 4.4.16, 4.5.9 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| joinmastodon mastodon | v < 4.3.22, 4.4.0 ≤ v < 4.4.16, 4.5.0 ≤ v < 4.5.9 | 4.3.22, 4.4.16, 4.5.9 |
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