High severity · published Apr 23, 2026
CVE-2026-41259
Mastodon: Insufficient verification of email addresses
7.5
CVSS
0.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 12% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MA
mastodon · mastodon
< 4.3.22; >= 4.4.0-beta.1, < 4.4.16; >= 4.5.0-beta.1, < 4.5.9 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-41259
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-41259
Vendor Advisory
https://github.com/mastodon/mastodon/security/advisories/GHSA-5r37-qpwq-2jhh
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