# CVE-2026-41259

## Summary

- **CVE ID:** CVE-2026-41259
- **Severity:** HIGH
- **CVSS Score:** 8.2 (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)
- **CWE:** CWE-841
- **Published:** Apr 23, 2026
- **Last Modified:** Apr 23, 2026

## 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.

## Affected Products

- mastodon — mastodon (< 4.3.22)
- mastodon — mastodon (>= 4.4.0-beta.1, < 4.4.16)
- mastodon — mastodon (>= 4.5.0-beta.1, < 4.5.9)

## References

- [CNA](https://github.com/mastodon/mastodon/security/advisories/GHSA-5r37-qpwq-2jhh)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.21%
- **EPSS Percentile:** 11.6

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._