Mastodon is a free, open-source social network server based on ActivityPub.

Code

The project this record applies to. Exploit listings stay in References.

• Repository · github.com

Timeline

Detection, updates, and resolution for this record.

1. Apr 23, 2026 · NIST NVD

   Detected

   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.

2. Jun 17, 2026 · NIST NVD

   Updated

   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.

Affected

• cpe joinmastodon/mastodonversion unspecified

Sources

• CVE.orgVulnerability recordCVE-2026-41259

  Official CVE identifier

  cve.org
• NIST NVDVulnerability recordCVE-2026-41259

  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 a

  nvd.nist.gov

References

• Vendor Advisory · github.com