CVE-2026-41259 PUBLISHED

Mastodon: Insufficient verification of email addresses

Assigner: GitHub_M
Reserved: 18.04.2026 Published: 23.04.2026 Updated: 23.04.2026

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.

Metrics

CVSS 4.0

CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
CVSS Score: 8.2

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	None	Confidentiality	None
Attack Complexity	Low	Integrity	High	Integrity	None
Attack Requirements	Present	Availability	None	Availability	None
Privileges Required	None
User Interaction	None

CVSS 4.0

Product Status

Vendor	mastodon
Product	mastodon
Versions	Version < 4.3.22 is affected Version >= 4.4.0-beta.1, < 4.4.16 is affected Version >= 4.5.0-beta.1, < 4.5.9 is affected

References

https://github.com/mastodon/mastodon/security/advisories/GHSA-5r37-qpwq-2jhh

Problem Types

CWE-841: Improper Enforcement of Behavioral Workflow CWE