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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.

PUBLISHED Reserved 2026-04-18 | Published 2026-04-23 | Updated 2026-04-23 | Assigner GitHub_M




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

Problem types

CWE-841: Improper Enforcement of Behavioral Workflow

Product status

< 4.3.22
affected

>= 4.4.0-beta.1, < 4.4.16
affected

>= 4.5.0-beta.1, < 4.5.9
affected

References

github.com/...stodon/security/advisories/GHSA-5r37-qpwq-2jhh

cve.org (CVE-2026-41259)

nvd.nist.gov (CVE-2026-41259)

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